Problems with FBH

[vindaloo]

I have a factory fitted FBH on my CDT Tourer, which when fired up by the usual test method (wire pin 3 to ground) and being invoked by a T4 bursts into life, but when the temperature was 4C this morning it didn't work when I drove off and still wasn't working when I arrived ay my destination, any ideas please?

[rich17865]

I have a factory fitted FBH on my CDT Tourer, which when fired up by the usual test method (wire pin 3 to ground) and being invoked by a T4 bursts into life, but when the temperature was 4C this morning it didn't work when I drove off and still wasn't working when I arrived ay my destination, any ideas please?

Maybe a t4 session will tell?

[HarryM1BYT]

I have a factory fitted FBH on my CDT Tourer, which when fired up by the usual test method (wire pin 3 to ground) and being invoked by a T4 bursts into life, but when the temperature was 4C this morning it didn't work when I drove off and still wasn't working when I arrived ay my destination, any ideas please?

Most likely, is that the thermal switch, which is visible through the front grill is badly calibrated. Perhaps it will not trigger until < 3C. They are known for being inaccurate.

Why not add a manual switch as per my how to below and the LED's, you can then have the car warm before you drive it?

[Unclefista]

Does pin 1 receive +12v when ignition is on and temp below five degrees ?

[vindaloo]

Does pin 1 receive +12v when ignition is on and temp below five degrees ?

No idea:getmecoat:

[rich17865]

There is a possibility it might still be faulty even though when forced it fires up, I think you should ask the fbh guru FrenchMike.

[FrenchMike]

Does pin 1 receive +12v when ignition is on and temp below five degrees ?

Hi all,

Not enough ,the engine is supposed running (+12 from alternator)

Anyway,if the FBH starts by connecting and kepping pin3 to:

+12 (first model)
earth (second model)

Then,it's ruled out;

rest ,the 5 degrées thermal switch or wiring.

Mike

[HarryM1BYT]

There is a possibility it might still be faulty even though when forced it fires up, I think you should ask the fbh guru FrenchMike.

If it definately fires up under test, as in the exhaust getting hot and if maintained running long enough, the water - then there is nothing at all wrong with the FBH.

It has to be the thermal switch or its wiring. The easy way to test the switch, even when it is too warm for it to switch on, is to start the engine then spray the sensor with a chiller spray through the grill. Mine switches on at < 4C.

The mod I suggest in my how to below, not only gives you full control, enabling you to run it without the engine - but the LED's also provide good feedback on what the FBH is actually doing and serve as a good diagnostic aid.

[vindaloo]

If it definately fires up under test, as in the exhaust getting hot and if maintained running long enough, the water - then there is nothing at all wrong with the FBH.

It has to be the thermal switch or its wiring. The easy way to test the switch, even when it is too warm for it to switch on, is to start the engine then spray the sensor with a chiller spray through the grill. Mine switches on at < 4C.

The mod I suggest in my how to below, not only gives you full control, enabling you to run it without the engine - but the LED's also provide good feedback on what the FBH is actually doing and serve as a good diagnostic aid.

Hi Harry, I have a bit more information, just popped into my friend's garage & tried a few things.

1. Froze the sensor down to -14degC, still nothing.
2. Pin 1 of the 6 pin does not measure any voltage, just a low pulse type reading with occasional earth pulses.
3. The large connector with Orange/Red (OR) & Black (B), should this be 12V switched & ground? If that's correct B does show ground but the OR has no voltage showing just a slight 'pulse' reading. If the FBH is not receiving 12V, why does it work when pin3 is grounded?

Apologies if this is not particularly clear as wiring is not my strong point, in truth nothing mechanical is either:getmecoat:

[Best_of_British]

I have exactly the same problem, followed Harry's excellent guide :bowdown: and now it works a treat when paper clip shoved in pin 3. Ive been looking forward to the first frost to see it in action and it fails to start :shrug:. Your problem appears to be the same as mine, has anyone got a link or part No. for the FBH sensor as im going to start with this and check the wiring.

However the more I think about it, it may make more sense and be cheaper to just put some sort of manual switch on it.

[vindaloo]

I have exactly the same problem, followed Harry's excellent guide :bowdown: and now it works a treat when paper clip shoved in pin 3. Ive been looking forward to the first frost to see it in action and it fails to start :shrug:. Your problem appears to be the same as mine, has anyone got a link or part No. for the FBH sensor as im going to start with this and check the wiring.

However the more I think about it, it may make more sense and be cheaper to just put some sort of manual switch on it.

If I don't have 12V available at the connections, I don't think a switch will help, but perhaps my assumptions are not correct.

[HarryM1BYT]

QUOTE=vindaloo


1. Froze the sensor down to -14degC, still nothing.

OK
2. Pin 1 of the 6 pin does not measure any voltage, just a low pulse type reading with occasional earth pulses.

Those reading might just be a bit of stray pickup from the wiring.

3. The large connector with Orange/Red (OR) & Black (B), should this be 12V switched & ground? If that's correct B does show ground but the OR has no voltage showing just a slight 'pulse' reading. If the FBH is not receiving 12V, why does it work when pin3 is grounded?

If the Orange/Red is the thick wire of the 2pin plug, then it should always have 12v on it, it is a permanent live fed directly off fuse #8. So I can only assume your measurement technique was at fault there.

If it fires up at all whn pin 3 is grounded, then its 12v must be good.

It is all pointing towards your +5C stat having failed or the wiring of the stat. The best way around it is to install manual control, the LED's and remember to turn it off. But not easy not to notice the LED's flasing :D

.

[vindaloo]

QUOTE=vindaloo


1. Froze the sensor down to -14degC, still nothing.

OK
2. Pin 1 of the 6 pin does not measure any voltage, just a low pulse type reading with occasional earth pulses.

Those reading might just be a bit of stray pickup from the wiring.


Understood

3. The large connector with Orange/Red (OR) & Black (B), should this be 12V switched & ground? If that's correct B does show ground but the OR has no voltage showing just a slight 'pulse' reading. If the FBH is not receiving 12V, why does it work when pin3 is grounded?

If the Orange/Red is the thick wire of the 2pin plug, then it should always have 12v on it, it is a permanent live fed directly off fuse #8. So I can only assume your measurement technique was at fault there.


Yes that's the one, definitely no voltage present on this, measurement method was sound, I think?


If it fires up at all whn pin 3 is grounded, then its 12v must be good.

I agree but still confused why pin 1 has no 12V present

It is all pointing towards your +5C stat having failed or the wiring of the stat. The best way around it is to install manual control, the LED's and remember to turn it off. But not easy not to notice the LED's flasing :D

.
If the stat has failed, the manual switch wouldn't work would it?


Comments above and apologies for my lack of knowledge.

[HarryM1BYT]

If I don't have 12V available at the connections, I don't think a switch will help, but perhaps my assumptions are not correct.

The switch only does exactly the same as the test, shorting pin 3 to ground - a switch should therefore work fine.

[HarryM1BYT]

It is all pointing towards your +5C stat having failed or the wiring of the stat. The best way around it is to install manual control, the LED's and remember to turn it off. But not easy not to notice the LED's flasing :D

.
If the stat has failed, the manual switch wouldn't work would it?

Comments above and apologies for my lack of knowledge.

A failure of the stat (or the stat wiring) has absolutely no bearing on whether the switch would or would not work.

The switch works just like the test, by shorting pin3 to ground. If the test works the switch will also work, no difference between the two.

[vindaloo]

A failure of the stat (or the stat wiring) has absolutely no bearing on whether the switch would or would not work.

The switch works just like the test, by shorting pin3 to ground. If the test works the switch will also work, no difference between the two.

Thanks for clearing that up Harry.

[HarryM1BYT]

A Basic Manual Override

The circuit below provides manual on/off control of te FBH, irrespective of whether the ignition is on or the +5C stat by the front bumper is calling for the FBH to run. An LED (LED1) warning light is included, to help you avoid the FBH being left on.


The second part of the circuit (LED2), provides an indication in the way of a brief flash from LED2 each time the FBH pump is triggered. The idea is to provide confirmation that the FBH is not only turned on, but that it is actually firing and the frequency of the flashing provides some useful feedback on how hard the FBH is working. The more frequently it flashes, the harder the FBH is working. Once the FBH shuts its self down a 77C, the flashing should stop. This part might be worth adding to those systems which already include a timer system or a remote control, even if a manual control is not needed. An alternative way to have done this, would have been to use the water pump feed as indication, but the water pump's running is not proof that the FBH is burning, nor would it give any clue as to how hard the FBH is running.

The items to the right hand side of the diagram below go in the cabin control (switch and LEDs). I made up a small plastic L shaped bracket, which I fixed close to the bonnet release pull. The two resistors are best mounted close to where the FBH plug wiring is tapped into. Wiring from the FBH to the control can be done in thin LAN type multi-core, it carries just milli-amps. The LED's MUST be connected with the correct polarity. All of the parts needed should be available from the likes of Maplins etc..

The switch is a tiny two pole one way toggle switch.
R1 and R2 are 2x 470Ohm
LED1 and LED2 are 2x superbright 3mm white LED's


http://i455.photobucket.com/albums/qq276/harrym1byt/FBHCircuit2.jpg
A= Connects to pin 3 of the FBH 6 pin
B= tapped onto +12 of the FBH 2 pin
C= Ground connection of the FBH 2 pin
D= Pump connection pin 6 on FBH 6 pin plug

FBH manual switch at the bottom, LED 1 on left above it and LED 2 above it on right. Above those, is the Synergy remote control. All mounted in the bonnet & boot release panel. Not easy to reach on the move, but still reachable.

[rich17865]

Water may have corroded the pins of the outdoor temperature sensor and be giving spurious readings. Might be worth removing and checking and or cleaning.

[vindaloo]

Water may have corroded the pins of the outdoor temperature sensor and be giving spurious readings. Might be worth removing and checking and or cleaning.

Wouldn't the normal temp readouts be haywire in that case, because they are not:getmecoat:

[HarryM1BYT]

Wouldn't the normal temp readouts be haywire in that case, because they are not:getmecoat:

It doesn't give 'readings' it is a simple thermal switch, it closes as the temperature falls, opens as it rises. It has nothing to do with the temperature sensor which feeds the dash gauge.

12v is fed to the FBH's thermal switch when the engine is running, if the temperature falls below 4C the switch closes, which then feeds 12v to the FBH to tell it to fire. If the coolant is less than 77C, then the FBH should then run to heat the coolant up to 77C.

[rich17865]

Where is this switch?

[oldcarguy]

Thermal switch is on the power steering fluid cooler rail which runs across the front of the radiator, on the left as you look from the front.

[rich17865]

Thermal switch is on the power steering fluid cooler rail which runs across the front of the radiator, on the left as you look from the front.

Got to be worth checking that it is connected, and or shorting it out to see if the fbh fires. A faulty switch is easily replaced. Even putting freezer spray on it with a multimeter attached to see if it works.

[oldcarguy]

I have the same problem as vindaloo and Best of British, after fitting the FBH and having the PCB sorted by FrenchMike, it fires up and runs great by earthing pin 3, but has yet to fire up on a cold morning. I had the bumper off last week and popped the sensor in the freezer for a while, and then did a ohms test on it, and it was working, but couldnt get my lazer tester to read properly, so dont know how cold it was. I was going to pop the bumper off again, but there seems to be little point if I dont have a replacement. Dont really want to pay £50 on the off chance, so its a trip to the breakers.

[rich17865]

I have the same problem as vindaloo and Best of British, after fitting the FBH and having the PCB sorted by FrenchMike, it fires up and runs great by earthing pin 3, but has yet to fire up on a cold morning. I had the bumper off last week and popped the sensor in the freezer for a while, and then did a ohms test on it, and it was working, but couldnt get my lazer tester to read properly, so dont know how cold it was. I was going to pop the bumper off again, but there seems to be little point if I dont have a replacement. Dont really want to pay £50 on the off chance, so its a trip to the breakers.

You don't need to get the bumper off, it is easily accessible with the undertray dropped.

It is an expensive part new, a breakers is your best bet.

[HarryM1BYT]

You don't need to get the bumper off, it is easily accessible with the undertray dropped.

It is an expensive part new, a breakers is your best bet.

It is only a thermal switch which is supposed to close at less than 5deg C. Maybe an standard part could be used at a £ or two?

Maybe this item on ebay-
Item number 150711331783

[oldcarguy]

Just been reading up on the thermal sensor, and apparently the Landrover one is more accurate( and is a recommended upgrade for our cars) and around half the price, so will see what the scrappy has in.

[dan_storm]

Does anyone have more info on the Land Rover part? Is it this part: http://www.rimmerbros.co.uk/Item--i-JWL000020 ?

Is it proven to work? Seems a lot cheaper than the rover part....

[oldcarguy]

Thats it, JWL000020. I have ordered one from Rimmers & one from a LR dealer, so we will see if they can get them, the LR dealer wasn't to sure whether they still supply them.
Apparently they are more accurate than the original sensor, and about half the price.

[dan_storm]

Just to update, I got a new Land Rover thermal sensor (with the part number above). It worked a treat and the FBH kicked in this morning when the ambient temperature was about 4 degrees.