A different CDTi fan problem

[RayH]

In a nutshell 2 speed fan with neither speed working, fan runs if you apply 12v directly.

A bit of background, I bought the car recently and noticed no low speed fan, didn't try high speed at that point.

A couple of weeks ago I took of the silver resistor, found it to be open circuit and replaced it. Re-assembled, still not working, bridged trinary switch - nothing! :eek:

As the car isn't my daily I got around to having another look today.
Stripped it out and found if you apply 12v to fan it runs, so no motor issues.

I have 12v on the connector in the wing, so fuse okay and ground on the other connector. I have checked the relays in the fan control box, by removing them and testing with 12v to coil and continuity across switched contacts.

So what am I missing?
Am I right in thinking the trinary switch when bridged by-passes every other control, so I'm not looking at ECU or anything horrible?
The only thing left that I can think of is the PCB in the fan control box itself.

Your thoughts would be appreciated gents - thanks Ray

[RayH]

The other thing I forgot to mention, there is a relay in the fan control box with nothing connected to it.
I'm assuming they used the same box for the old 3 speed fan?

[FrenchMike]

What is marked on the resistor you have fitted ?

[RayH]

What is marked on the resistor you have fitted ?

Thanks for the response - it is
Arcol 11.41
HS100 R47 J

[bigbaldbloke]

Have you got 12V and ground at the control box itself? And while you're in the box, are the output wires to the fan and resistor showing closed circuit?

[FrenchMike]

Thanks for the response - it is
Arcol 11.41
HS100 R47 J

looks Correct ;could be a faulty relay ? or wrong connection ?

[RayH]

Have you got 12V and ground at the control box itself? And while you're in the box, are the output wires to the fan and resistor showing closed circuit?

Yes, I should have made that clearer.

In fact if I bridge the relays in turn I get slow speed and fast speed.

While back in there I checked the voltages on each of the relay coils and I have approx 5v on all of the coil contacts.

I didn't notice when I had them out earlier but do they operate on 5v or should there be 12v there?

This voltage is present on all relay coil contacts when the ignition is on, regardless of AC position even with the ATC turned off.

[RayH]

looks Correct ;could be a faulty relay ? or wrong connection ?

The relays checked out earlier but they are not being energised.

[T-Cut]

So what am I missing?

Fuse 4 in the engine fuse box?
RH row, second down.

TC

[RayH]

Fuse 4 in the engine fuse box?
RH row, second down.

TC
Nope, just been to check it again in case I did miss it :shrug:

[bigbaldbloke]

Yes, I should have made that clearer.

In fact if I bridge the relays in turn I get slow speed and fast speed.

While back in there I checked the voltages on each of the relay coils and I have approx 5v on all of the coil contacts.

I didn't notice when I had them out earlier but do they operate on 5v or should there be 12v there?

This voltage is present on all relay coil contacts when the ignition is on, regardless of AC position even with the ATC turned off.

Don't know about voltage, but I think the switching is on the ground side, so permanent live makes sense.

[FrenchMike]

Yes, I should have made that clearer.

In fact if I bridge the relays in turn I get slow speed and fast speed.

While back in there I checked the voltages on each of the relay coils and I have approx 5v on all of the coil contacts.

I didn't notice when I had them out earlier but do they operate on 5v or should there be 12v there?

This voltage is present on all relay coil contacts when the ignition is on, regardless of AC position even with the ATC turned off.

I think they need 12v to be energised (must be marked on them)

[RayH]

I think they need 12v to be energised (must be marked on them)
Yes, I need to pull them back out and have a look but presumably they wouldn't all energise at the same time so I must be missing a ground for the coils too?

[FrenchMike]

Yes, I need to pull them back out and have a look but presumably they wouldn't all energise at the same time so I must be missing a ground for the coils too?

I guess there is a 12v permanent on one side of the coil , the
other side being the earth return via the electronic device...:shrug:

You can short it to earth for test without damage .

[T-Cut]

The only thing left that I can think of is the PCB in the fan control box itself.

The problem smacks of a cryptic cause, which makes the PCB a favourite.

TC

[RayH]

The problem smacks of a cryptic cause, which makes the PCB a favourite.

TC
That's the way I'm leaning.
Ideally I'd like to know if the trinary switch bridge test is effectively direct to the fan control or via something else, such as ECU.
If it is direct then it would seen fairly conclusive :shrug:

[FrenchMike]

That's the way I'm leaning.
Ideally I'd like to know if the trinary switch bridge test is effectively direct to the fan control or via something else, such as ECU.
If it is direct then it would seen fairly conclusive :shrug:

From Rave,ECM controls the different speeds via a PWM signal .

Except the medium one via the trinary switch too:

http://rovermg1.free.fr/rovermg/thumbnails/DCeFNL4rt1GB4FvDSnWm.jpg (http://rovermg1.free.fr/rovermg/images/DCeFNL4rt1GB4FvDSnWm.jpg)

[SD1too]

The only thing left that I can think of is the PCB in the fan control box itself.
Correct Ray. You diagnosed this yourself in your first post. :D

... I checked the voltages on each of the relay coils and I have approx 5v on all of the coil contacts ... do they operate on 5v or should there be 12v there?
The relays are 12 volts.

... I'd like to know if the trinary switch bridge test is effectively direct to the fan control or via something else, such as ECU.
On the diesel, direct to the fan control box PCB as you correctly say.

Jules may be able to supply you with a replacement PCB.

Simon

[Mike Noc]

From Rave,ECM controls the different speeds via a PWM signal .

Except the medium one via the trinary switch too:

http://rovermg1.free.fr/rovermg/thumbnails/DCeFNL4rt1GB4FvDSnWm.jpg (http://rovermg1.free.fr/rovermg/images/DCeFNL4rt1GB4FvDSnWm.jpg)

Mike the power side of the RAVE circuit diagram is wrong. The high speed on the 3 speed diesel fan is achieved by an extra ground to the motor.

Here is a sketch from when I had mine apart:

http://i1108.photobucket.com/albums/h415/MikeNoc/Rover75CDT3SpeedCoolingFan_zpsba70bfd0.jpg (http://s1108.photobucket.com/user/MikeNoc/media/Rover75CDT3SpeedCoolingFan_zpsba70bfd0.jpg.html)

[RayH]

From Rave,ECM controls the different speeds via a PWM signal .

Except the medium one via the trinary switch too:

http://rovermg1.free.fr/rovermg/thumbnails/DCeFNL4rt1GB4FvDSnWm.jpg (http://rovermg1.free.fr/rovermg/images/DCeFNL4rt1GB4FvDSnWm.jpg)

Thanks for that, so if I'm right in my thinking for the 2 speed fan, the signal from the trinary is direct to the fan control. So if I ground that tomorrow and it still doesn't run then it must be the pcb in the fan control?

Cheers Mike it is getting more hopeful :}

[RayH]

Mike the power side of the RAVE circuit diagram is wrong. The high speed on the 3 speed diesel fan is achieved by an extra ground to the motor.

Here is a sketch from when I had mine apart:

http://i1108.photobucket.com/albums/h415/MikeNoc/Rover75CDT3SpeedCoolingFan_zpsba70bfd0.jpg (http://s1108.photobucket.com/user/MikeNoc/media/Rover75CDT3SpeedCoolingFan_zpsba70bfd0.jpg.html)

Hopefully my thinking is still valid as far as the trinary switch being direct to the PCB though?

[RayH]

Correct Ray. You diagnosed this yourself in your first post. :D


The relays are 12 volts.


On the diesel, direct to the fan control box PCB as you correctly say.

Jules may be able to supply you with a replacement PCB.

Simon

Thank you Simon, now I'm really happy :D

[SD1too]

... the signal from the trinary is direct to the fan control. So if I ground that tomorrow and it still doesn't run then it must be the pcb in the fan control?
Ray,

Just to be clear; the trinary medium pressure switch earths the YS (yellow/grey) wire from the fan control box PCB to trigger a higher fan speed.

Simon

[RayH]

Ray,

Just to be clear; the trinary medium pressure switch earths the YS (yellow/grey) wire from the fan control box PCB to trigger a higher fan speed.

Simon

Excellent, yes I think that is what I was trying to say. I'll do one last check by grounding that then it has to be the PCB. :}

[RayH]

Okay final test completed, grounding the slate wire on the PCB, which comes from Yellow/Slate trinary switch, has no effect.
Conclusion - PCB faulty.
Remedy - PM coming your way Jules :D

Once again many thanks for keeping my thinking straight and supplying the diagrams.

[Jules]

All PWM pcb's sold out sorry chaps.

If anyone comes across them grab them as they are like hens teeth.
Breakers on here may be able to help :shrug:

[Billy1mate]

I think I have 1 possibly 2, I'll have a look in the morning.

[RayH]

I think I have 1 possibly 2, I'll have a look in the morning.

Thank you I'd be obliged :}

[bigbaldbloke]

And I may be after you for the (possible) second after tomorrow - Greeners and I are stripping my fan down to sort, PCB failure can't be ruled out yet.

[Alan123]

Nope, just been to check it again in case I did miss it :shrug:

Fuse 4 in the under bonnet fuse box is for the auto box if I'm correct :shrug:

[RayH]

Fuse 4 in the under bonnet fuse box is for the auto box if I'm correct :shrug:

That as well by the looks of things :D

From the manual
"Automatic transmission, air conditioning, cooling
fan, cruise control (diesel models)"

[RayH]

Many thanks to Steve (Arctic) for finding me one of these, and to the others who offered to look, you can stop looking now chaps :D

[RayH]

Okay some progress along with some disappointment.

PCB arrived this morning - cheers Steve.
Weather appalling but cleared later so out I go.

Fit PCB but, fortunately, left it all out on the ground to test.
Demist test, yippee fan running but hang on that's rather fast, fan is running at second speed. On checking both the low and high relays are being energised.

Turn off demist and bridge trinary - nothing :eek:

Had another look on here and found this http://www.the75andztclub.co.uk/forum/showthread.php?t=218080&page=2 and noted that although I have a 2 speed fan my wiring, which looks original, is wired as a 3 speed with regard to the control wires. But obviously nothing connected to the third relay.

So I rewire as per the photo for 2 speed and now I get response to bridging the trinary, naturally, but still high speed on demist.

If I take the return off the high speed relay then the low speed works. So that rules out the resistor being wired incorrectly.

Rain stop play again at the moment but wondering what should be happening for low speed. Does the ECM put low votage to the fan PCB rather than grounding it but then grounds it if it calls for high speed.

The other thing I noticed afterwards is that there are a couple of components missing of the original PCB, in fact they look to have been removed rather than not fitted. Was this some sort of hybrid board and wiring arrangement that utilised the red/blue and grey wires separately?

This was the original wiring
http://1drv.ms/1MDzEdP

These are the boards with the components missing/removed ringed on the original
http://1drv.ms/1MDzTWg

Your thoughts welcomed as always.

Looking at those photos again there are a couple more components missing that I haven't circled.

[Jules]

Have you fitted the correct PCB?

3 speed PCB's switch the large relay for LOW speed.

The later 2 speed PCB's use the middle small relay for LOW speed.
Large relay is for HIGH speed.

No problem using incorrect PCB, just swap the thick red and grey wires over in the control box.

[Greeners]

how many wires has the fan got ?

Courtesy of Stocktake (Thanks Dave )

http://i242.photobucket.com/albums/ff289/stocktake/dieselthreespeedwiringwithtwospeedfan.jpg

[Greeners]

I've just sorted out this mess (http://www.the75andztclub.co.uk/forum/showthread.php?t=221386)

[SD1too]

Courtesy of Stocktake (Thanks Dave )

http://i242.photobucket.com/albums/ff289/stocktake/dieselthreespeedwiringwithtwospeedfan.jpg
David,

The above diagram shows the red and grey relay contact wires the wrong way around; see thread "3 speed fan dead" by johnandchris 26.09.14. Stocktake is aware. It's probably best to avoid publishing this diagram whenever possible.

Union Wheels has posted a different solution here (http://www.the75andztclub.co.uk/forum/showthread.php?t=209920).

Simon

[RayH]

Thanks Jules, David, Simon and Steve by PM.

I did check in case I was that boggled last night, but it matters not which relay I put the red and grey on.
Both relays are energised when I use demist!

They are actually being energised, if I remove the thick red and black, switch to demist and check continuity across relay contacts then they are made, if I turn of demist they are open.

If I remove the thin grey wire, coming from trinary, completely, the effect is the same.

I have a 2 speed, 2 wire fan with resistor, and the PCB has the same, 194/5, markings on it. However, as mentioned in previous post, the original board appears to have been modified by component removal.
I'm not sure if this was an elaborate "bodge" to overcome the problem of the fan running on high with A/C, or a legitimate mod.
I'd have thought that anyone with enough knowledge to carry out that mod would have realised that isolating the high speed relay would have had the same effect :shrug:

I did pose a question to Steve regarding the coolant temp sensor, basically if this were faulty would it give me this?

Many thanks
Ray

[Arctic]

Have you fitted the correct PCB?

3 speed PCB's switch the large relay for LOW speed.

The later 2 speed PCB's use the middle small relay for LOW speed.
Large relay is for HIGH speed.

No problem using incorrect PCB, just swap the thick red and grey wires over in the control box.

Hi Ray.
As above and my reference to you in the PM take a look at your control box wiring layout which doe's if resemble from the pics below
http://i40.tinypic.com/xkvkwh.jpg

grey and red wires swapped over
http://i58.tinypic.com/2i1i5y1.jpg

Note the thin wires in your control box also.
http://i46.tinypic.com/242sfmu.jpg

This control box is from an ebay aftermarket fan which I doubt your would be like anyways.
http://i47.tinypic.com/mvqh3t.jpg

[RayH]

Hi Ray.
As above and my reference to you in the PM take a look at your control box wiring layout which doe's if resemble from the pics below



This one originally
http://i46.tinypic.com/242sfmu.jpg

After seeing one of your other threads I changed to this,
The only difference that made was the trinary test then worked.
http://i40.tinypic.com/xkvkwh.jpg

In relation to the thick Red and Grey wires - either way makes no difference as both relays are being energised together, the only one that isn't is the far left (unused) one.

[Arctic]

Hi Ray
I am off out is a bit in the meantime can you pop a photo up of your control box, and also check all the wires coming from the fan motor to control box and from control box to the end loom plugs if you have not done so already, this is just to make sure one of the joints as not corroded.

Also have you changed moved the thin grey wire and added it to the thin blue /red wire ? if so try putting them back as below and see what happens then.

http://i46.tinypic.com/242sfmu.jpg

[RayH]

Hi Ray
I am off out is a bit in the meantime can you pop a photo up of your control box, and also check all the wires coming from the fan motor to control box and from control box to the end loom plugs if you have not done so already, this is just to make sure one of the joints as not corroded.

Also have you changed moved the thin grey wire and added it to the thin blue /red wire ? if so try putting them back as below and see what happens then.

http://i46.tinypic.com/242sfmu.jpg

Cheers Steve, yes I'm off shortly too until late tonight.
Picture of box here http://1drv.ms/1MDzEdP

Yep, checked fan motor to box and back to plugs, and both speeds will work (if I disconnect the high speed relay I get low, and if I reconnect I get high).

Yes, have tried grey (thin) wire on its own, as was, and coupled with blue/red. The only difference was that on its own the trinary test did nothing, but joined with blue/red it gave me high speed. There again everything gives me high speed :}.

I have checked the thin wires back from the box to the plug.
Further, if I disconnect both the grey and the red/blue but leave the black and yellow connected then the relays are off, as you'd expect.
If I replace the red/blue and switch on demist then both relays energise to give me high speed. If I then remove red wire from relay I get low speed via the resistor.

Ray

[SD1too]

Both relays are energised when I use demist!
Ray; I think that this must mean that the PCB you are using is faulty.
.. the original board appears to have been modified by component removal.
Yes, it appears that the PCB manufacturer modified the original 3 speed design to work with a 2 speed circuit by removing components. I worked this out with the generous help of Steve (Arctic) who supplied masses of photographs of both sides of various PCBs.

Simon

[RayH]

Ray; I think that this must mean that the PCB you are using is faulty.

Yes, it appears that the PCB manufacturer modified the original 3 speed design to work with a 2 speed circuit by removing components. I worked this out with the generous help of Steve (Arctic) who supplied masses of photographs of both sides of various PCBs.

Simon

I hope you are right as the only alternstive I can think of is the ECU switching to high speed for cooling but in that case it wouldn't wait for the AC to be turned on?

I've got someone sending me another to try so I'll keep you updated.
Once again thank you all for your help.

Ray

[Arctic]

Ray; I think that this must mean that the PCB you are using is faulty.

Yes, it appears that the PCB manufacturer modified the original 3 speed design to work with a 2 speed circuit by removing components. I worked this out with the generous help of Steve (Arctic) who supplied masses of photographs of both sides of various PCBs.

Simon


Simon.
I have just been taking some photo's of the PCB boards trying to show the differing components which I think you are referring too I am uploading them now to my bucket etc if you would like them sent to please drop me a email cheers Arctic.

PS
Maybe Ray need the dark green one or if you could Ray please pop up a pic of your original PCB board showing the back as I have.

[RayH]

Simon.
I have just been taking some photo's of the PCB boards trying to show the differing components which I think you are referring too I am uploading them now to my bucket etc if you would like them sent to please drop me a email cheers Arctic.

PS
Maybe Ray need the dark green one or if you could Ray please pop up a pic of your original PCB board showing the back as I have.

Hi Steve

No it wasn't the dark green, I did post links to some pictures earlier in this thread post #33
http://1drv.ms/1MDzTWg
When it opens click on View Original for a slightly larger one.

Simon - I reckon there are 5 components that have been removed, were you able to establish if any others have been changed. I've proposed, to Steve, that I remove those components and we'll see where that takes us.

Ray

[Arctic]

Hi Steve

http://1drv.ms/1MDzTWg
When it opens click on View Original for a slightly larger one.

Simon - I reckon there are 5 components that have been removed, were you able to establish if any others have been changed. I've proposed, to Steve, that I remove those components and we'll see where that takes us.

Ray

Hi Ray.
Having double checking again a few times yes I can only see 5 components that have been changed pics below ;)

One top middle Fig 1
http://i58.tinypic.com/29n8b5f.jpg1

Centre of the board Fig 2
http://i59.tinypic.com/dpjz8m.jpg2

Comparison of top middle Fig 3
http://i59.tinypic.com/15nu6p0.jpg

Comparison of centre board Fig 4
http://i62.tinypic.com/2v8kazd.jpg4

Top right of board Fig 5
http://i60.tinypic.com/2s7xmas.jpg5

Comparison top right Fig 6
http://i61.tinypic.com/2yxoo6h.jpg6

Bottom left two components in the same area Fig 7
http://i58.tinypic.com/1z1zj37.jpg7

Comparison bottom left Fig 8
http://i58.tinypic.com/4fx1lw.jpg8

Two boards together Fig 9
http://i58.tinypic.com/jaat90.jpg9
Arctic ;)

[SD1too]

If I replace the red/blue and switch on demist then both relays energise to give me high speed.
As I'm sure you know Ray, this wire carries a pulse width modulated signal from the ECM which is decoded by the PCB. 'Demist' should normally trigger the slow speed.

... the only alternstive I can think of is the ECU switching to high speed for cooling but in that case it wouldn't wait for the AC to be turned on?
Correct. Or, if the refrigerant pressure is too high, the 'demist' button will run the slow speed but the trinary switch will also cause the high speed relay to operate. Removing the trinary grey wire from the PCB should then cause the PCB to revert to slow speed, if all is well.

I've proposed, to Steve, that I remove those components and we'll see where that takes us.
:eek: I would keep all your boards intact Ray. Other component values may have been changed on the modified boards, and the ICs may have been programmed differently.

On the 2 speed board, is the right hand small relay coil (high speed in 3 speed mode) isolated by means of component removal? It was on the sample which Steve (Arctic) showed me.

Simon

[RayH]

Removing the trinary grey wire from the PCB should then cause the PCB to revert to slow speed, if all is well.

Yes, I should have said, trinary was unplugged. So demand for high speed not coming from there.


:eek: I would keep all your boards intact Ray. Other component values may have been changed on the modified boards, and the ICs may have been programmed differently.


That's what I was hoping to establish, but I take your point :D

My original board has undergone post-production modification, unlike the photo of Steve's where the solder pads are unused.

If you look at mine in post #33 you can clearly see that they were removed. There is little evidence of anything else but I will have a much closer look, component by component tomorrow.



On the 2 speed board, is the right hand small relay coil (high speed in 3 speed mode) isolated by means of component removal? It was on the sample which Steve (Arctic) showed me.

Simon

Yes

Will not be much happening today, but I hope to make some progress with this tomorrow.

Ray

[SD1too]

Yes, I should have said, trinary was unplugged. So demand for high speed not coming from there.
:D You're doing a great diagnostic job Ray.

Simon

[RayH]

:D You're doing a great diagnostic job Ray.

Simon

I get by with a lot of help from my friends
To paraphrase some old band :bowdown:

[FrenchMike]

Hi Guys,

The IC is a quadruple comparator (simply) LM 2901

Upload the datasheet and try to build up the drawing around .
It could help :}

Mike

[RayH]

Hi Guys,

The IC is a quadruple comparator (simply) LM 2901

Upload the datasheet and try to build up the drawing around .
It could help :}

Mike

Thanks Mike but I think I'll need to leave that bit to someone else :D
Quite happy to send you a non-working board when I've finished though if you are interested.

Ray

[FrenchMike]

Thanks Mike but I think I'll need to leave that bit to someone else :D
Quite happy to send you a non-working board when I've finished though if you are interested.

Ray

No prob Ray,curious to know what component fails on these PCBs ....:}

Mike

[RayH]

Right then gents I think we have done it :}

Looked closely at the two boards this morning and, apart from the five components that were removed, I not convinced there weren't some other differences. However, I decided on the adventurous approach and removed said five components!

Tested off car tuned on AC - HIGH SPEED :mad:

Remained logical and checked relays, only one was closing now - excellent - but not the one currently wired to resistor, so they needed reversing. This is an extra bit of work for later as it involves extending that lead.
Reversed leads - slow speed.

Next step, bridge trinary, no effect at all, so joined thin grey to red/blue and retest - yes! High speed.

Final test with AC off remove connector to coolant sensor - high speed again, with fan continuing to run with ignition off until sensor re-connected.

Needs a bit or wiring tidied up and refitting but more than happy this afternoon :D :D

I'm still trying to get my head around what MAY have happened in the past as clearly some work, or at least investigation, has been done previously. One of the release tabs on the main connectors in the wing is snapped. We will probably never know.

Once again thanks for all your help.

Ray

[SD1too]

Well done Ray! :clap:

I remain rather confused about all the PCBs you've had though.:o Was the original, which didn't work, the 2 speed type with removed components? If so, then it looks like the problem was getting the grey wire from the trinary switch in the right place and transposing the relay contact heavy duty wires. Have I got that right?

Out of interest, which colour is now in the resistor circuit, red or grey?

Simon

[RayH]

Well done Ray! :clap:

I remain rather confused about all the PCBs you've had though.:o Was the original, which didn't work, the 2 speed type with removed components? If so, then it looks like the problem was getting the grey wire from the trinary switch in the right place and transposing the relay contact heavy duty wires. Have I got that right?

Out of interest, which colour is now in the resistor circuit, red or grey?

Simon

Thanks Simon :D

You are confused? What about me? :getmecoat:

My original is here http://1drv.ms/1MDzEdP and this is the same as Steve's picture in post #41. Which would appear to be 3 speed with components removed but I can't say with certainty as I haven't actually seen a 3 speed PCB, although the signs are that it is.

The problem was not just reversing the red and grey wires, this had been tried following advice from Steve, but with the five "additional" components both relays were being energised together.

The thin grey wire, from the trinary, did not activate the fan in the position pictured above. I am inclined to think that it wouldn't have done so on my original board :eek:

The final, working, setup looks like the second picture in post #39 but it would not work correctly whilst those five components were in place.

I could be barking up the wrong tree, in the wrong forest even, but based on what I have seen I can imagine the following scenario.

2 speed fan introduced and PCB is modified (by component removal). The wiring loom is also modified by linking grey and red/blue.
At some point, either in production or a later attempted repair, a modified PCB is fitted to an unmodified loom.
Providing the fan grey and red are correct on the relays the only bit missing would be the trinary over pressure link.

I come along and find no fan function at all due to PCB failure and obtain a replacement. However this has not been modified so would presumably operate normally in a 3 speed setup?

The rest as they say ...........

I'm wondering if anyone else has tried to replace the PCB and ended up with peculiar results and possibly not noticed them.

Unless they tested it they would be unlikely to notice the trinary over pressure function was not working and possibly they may not be aware the fan was running at full speed with AC on. It may even have been put down to "It's working properly now, you can hear it!"

I hope that hasn't muddied the waters even more Simon :D

Incidentally, I have arranged with French Mike to send him the failed board. So we may hear more about this in the future.

[SD1too]

Thanks for your reply Ray. No, you haven't muddied the waters further. I think that you've come up with a very believable explanation.

Your experience is the best example yet of the folly of manufacturers pursuing technically sophisticated solutions when the traditional simpler principles would work just as well and be a whole lot more reliable. I mean, creating a PWM signal which they knew would be outside the expertise of dealers and has to be decoded by another circuit which no-one understands and is placed in a hostile environment for delicate electronics. All this just to trigger a couple of relays! It's madness. The petrol engine design achieves the same ends without the unreliability and mystery of the PWM circuit. As for splicing the trinary switched earth into the PWM input; well, that has all the hallmarks of a design bodge. What a mess! :getmecoat:
Incidentally, I have arranged with French Mike to send him the failed board. So we may hear more about this in the future.
I hope so. The more we learn about this the better.

Simon

[RayH]

Thanks for your reply Ray. No, you haven't muddied the waters further. I think that you've come up with a very believable explanation.

Your experience is the best example yet of the folly of manufacturers pursuing technically sophisticated solutions when the traditional simpler principles would work just as well and be a whole lot more reliable. I mean, creating a PWM signal which they knew would be outside the expertise of dealers and has to be decoded by another circuit which no-one understands and is placed in a hostile environment for delicate electronics. All this just to trigger a couple of relays! It's madness. The petrol engine design achieves the same ends without the unreliability and mystery of the PWM circuit. As for splicing the trinary switched earth into the PWM input; well, that has all the hallmarks of a design bodge. What a mess! :getmecoat:

I hope so. The more we learn about this the better.

Simon

I also wondered why it was so complicated compared to the petrol versions.
A couple of control wires to the relays and that would have been it, hey-ho as you say madness!

Once again thanks to everyone here for giving advice, and letting me bounce ideas off them.

Ray

[Jules]

The PWM PCB's are susceptible to damage when removing them from the relays.
No matter how careful and gradually they are removed from the tight fitting relay terminals odd faults can occur after refitting.

My guess is that the delicate surface mount components can get cracked or a solder joint broken.

The other theory is that one of the IC's is actually static sensitive and unless full SSD procedures are carried out, the board will be damaged just by touching it :shrug:


This is why we don't recommend diesel owners change the relays until a reliable source of spare PCB's is found.

The 100 or so boards I had from Longbridge have all been used up so they are like hens teeth now.

[RayH]

The PWM PCB's are susceptible to damage when removing them from the relays.
No matter how careful and gradually they are removed from the tight fitting relay terminals odd faults can occur after refitting.

My guess is that the delicate surface mount components can get cracked or a solder joint broken.

The other theory is that one of the IC's is actually static sensitive and unless full SSD procedures are carried out, the board will be damaged just by touching it :shrug:


This is why we don't recommend diesel owners change the relays until a reliable source of spare PCB's is found.

The 100 or so boards I had from Longbridge have all been used up so they are like hens teeth now.

You may well be right although I went over my old board with a jewellers loupe and found nothing obvious.
Also the static damage theory would not explain why the original board failed in the first place.

Perhaps French Mike can throw some light on it when he has examined my old board. It's probably held up in some French port as we speak :D

[Jules]

Apart from wear & tear of course.
Any electronics can fail at anytime with no notice especially in harsh environments such as in automobiles !

[RayH]

Apart from wear & tear of course.
Any electronics can fail at anytime with no notice especially in harsh environments such as in automobiles !

Absolutely and don't we know it!
In fact just replace "electronics" with "thing" in that statement :D

A bit OT (but it's my thread so I can ;)) did you sort out that pollution previously discussed?

[Jules]

Not yet Ray

[Union Wheels]

Very interesting read and well done for seeing the problem solved.

My own experience of the P.C board was after a bird strike which broke the fan blades.

Before I refitted the fan assembly I tested the relays by putting 12 volts across their coils, and then refitted the fan assembly, only to find that the slow speed did not work.

Upon further investigation one of the relay coil switching transistors had failed (surface mount PNP device had gone base/emitter short circuit). I had a quantity of BC327 transistors laying around and mounted one of these in place of the surface mount device. This solved the problem.

I think that testing the relays while still in circuit damaged this transistor due to the back EMF of the coil, and point this out as warning to anybody testing the relays in this way

Cheers, Pete.

[Jules]

My sentiments entirely Pete.
Don't test relays in circuit.

BC327's yum used plenty of those back in my TV repair days :drool4:

[FrenchMike]

Hi All,

I have received the PCB that RayH kindly has sent to me and i have learnt
a lot of things i would like to share..

Thread coming soon :}

Mike

[Arctic]

Hi All,

I have received the PCB that RayH kindly has sent to me and i have learnt
a lot of things i want to share..

Thread coming soon :}

Mike


Hi Mike.
I /we will look forward to a good read then :D Arctic

[FrenchMike]

Hi Mike.
I /we will look forward to a good read then :D Arctic

HERE IT IS:

http://www.the75andztclub.co.uk/forum/showthread.php?t=222452

All comments are welcome :D

Mike