Radiator Fan

[davidcarp]

My radiator fan has never worked on low or medium speeds and had no problems. My high speed came on if I switched on the A/C. Just got back from the shops and the high speed fan stays on even when I switch OFF. Its happened before but after a couple of minutes it goes off but not this time. I disconnected the battery and it went off. Looked at the circuit diagram and removed Fuse FL4. At least I don't have to keep disconnecting the battery. I've booked it in with my local mechanic. I know I'll probably need a new fan. Its old and hasn't got a resistor. Any ideas where I could get a replacement. I've read about get 2 speed and 3 speed fans. Are they interchangeable or need wiring change etc? Grateful for any assistance. Thanks

[Neil1]

My radiator fan has never worked on low or medium speeds and had no problems. My high speed came on if I switched on the A/C. Just got back from the shops and the high speed fan stays on even when I switch OFF. Its happened before but after a couple of minutes it goes off but not this time. I disconnected the battery and it went off. Looked at the circuit diagram and removed Fuse FL4. At least I don't have to keep disconnecting the battery. I've booked it in with my local mechanic. I know I'll probably need a new fan. Its old and hasn't got a resistor. Any ideas where I could get a replacement. I've read about get 2 speed and 3 speed fans. Are they interchangeable or need wiring change etc? Grateful for any assistance. Thanks

Contact Jules as he's the one that can help you with any issues.
http://www.the75andztclub.co.uk/forum/showthread.php?t=189409

[SD1too]

Hello David,

Before you speak to Jules let's make sure that we have the correct diagnosis because what you say isn't quite right.

My radiator fan has never worked on low or medium speeds and had no problems. My high speed came on if I switched on the A/C.
When you switch on the air con. it's the slow speed which starts running. The high speed on a 3 speed system is never triggered by the air con.
With the air con. operating, does the fan run continuously or does it cut in and out?
Just got back from the shops and the high speed fan stays on even when I switch OFF ... I disconnected the battery and it went off.
It's a pretty safe bet that you have PCB failure David. Does the fan stay running if you select 'Econ' on the air con. control panel?
I've booked it in with my local mechanic. I know I'll probably need a new fan.
Actually you probably won't (from what you've told me) so I'd cancel that booking. Your local mechanic will fit an MG Rover complete 2 speed fan system which will fail after a couple of years because the silver resistor is under-rated for the job. You will pay over £400 for this.
Its old and hasn't got a resistor.
So what? :D My 3 speed fan is old and hasn't got a resistor and it's fine. Come back to me with some more information David and the club will save you a lot of money.

Simon

[davidcarp]

Hello David,

Before you speak to Jules let's make sure that we have the correct diagnosis because what you say isn't quite right.


When you switch on the air con. it's the slow speed which starts running. The high speed on a 3 speed system is never triggered by the air con.
With the air con. operating, does the fan run continuously or does it cut in and out?

It's a pretty safe bet that you have PCB failure David. Does the fan stay running if you select 'Econ' on the air con. control panel?

Actually you probably won't (from what you've told me) so I'd cancel that booking. Your local mechanic will fit an MG Rover complete 2 speed fan system which will fail after a couple of years because the silver resistor is under-rated for the job. You will pay over £400 for this.

So what? :D My 3 speed fan is old and hasn't got a resistor and it's fine. Come back to me with some more information David and the club will save you a lot of money.

Simon

Thanks for the info. My car is a 'Classic' and is the basic A/C and doesnt have economy mode. As far as I know the fan stays on all the time with A/C on. If it is slow speed it makes a loud noise when operating. The auto electrician has been booked so he might find the cause. I wont change any thing in a hurry till I get advice. I've had the car 5 years without the fans working with no problems. I tried the demist button test and the fan didnt work. If it is the PCB where is it located and what is involved replacing it? Thanks

[SD1too]

My car is a 'Classic' and is the basic A/C and doesnt have economy mode.
Yes it does David. Press the 'A/C' button and you have air conditioning. Press it again and the air con. turns off; that's economy mode! :D It's no different from the ATC system.
As far as I know the fan stays on all the time with A/C on.
I suggest that you check it to be sure. It's crucial to a correct fault diagnosis.
I tried the demist button test and the fan didnt work.
With your system you need to turn the rotary air distribution control to the windscreen demist symbol. It's not a button. Did you do that?

Can you get back to me David asap? Thanks.

Simon

[davidcarp]

Yes it does David. Press the 'A/C' button and you have air conditioning. Press it again and the air con. turns off; that's economy mode! :D It's no different from the ATC system.

I suggest that you check it to be sure. It's crucial to a correct fault diagnosis.

With your system you need to turn the rotary air distribution control to the windscreen demist symbol. It's not a button. Did you do that?

Can you get back to me David asap? Thanks.

Simon

As the fan stays on all the time even with A/C off I cant really tell.After I turned the engine off fan stays on. I disconnected the battery as I had to go to work later and didn't want to flatten it. I reconnected it later and the fan came on again. Switched off and removed R4 relay in engine fuse box. Didn't work. Removed FL4 80 AMP and fan stayed off. As I said the auto electician will hopefully confirm the snag. If it is the PCB what are my options? I won't change anything till I get advice through the club. Thanks for your help

[SD1too]

... removed R4 relay in engine fuse box. Didn't work. Removed FL4 80 AMP and fan stayed off.
Thanks for this important evidence which tells me exactly what the problem is.
As I said the auto electician will hopefully confirm the snag.
David; I and everyone else in this club are very willing to pass-on our knowledge and experience of the 75/ZT to others who are in trouble and are seeking help, and our assistance is free. I hope that you can understand that, having spent time giving advice, your wish to consult an auto electrician tends to suggest that you don't really trust us here in the club. That's entirely your decision, but I'd prefer it if you could decide which way you want to go: club or trade? What I don't want to happen is for me to spend more time investigating and diagnosing your problem and then you say something like "thanks, but the auto electrician says that I need a new ECU", and believe me, I am not jesting!

I predict that your auto electrician won't be able to diagnose this one because the diesel fan circuit is very complicated and there are errors even in the MG Rover wiring diagram (which he won't have).

Simon

[Neil1]

Thanks for this important evidence which tells me exactly what the problem is.

David; I and everyone else in this club are very willing to pass-on our knowledge and experience of the 75/ZT to others who are in trouble and are seeking help, and our assistance is free. I hope that you can understand that, having spent time giving advice, your wish to consult an auto electrician tends to suggest that you don't really trust us here in the club. That's entirely your decision, but I'd prefer it if you could decide which way you want to go: club or trade? What I don't want to happen is for me to spend more time investigating and diagnosing your problem and then you say something like "thanks, but the auto electrician says that I need a new ECU", and believe me, I am not jesting!

I predict that your auto electrician won't be able to diagnose this one because the diesel fan circuit is very complicated and there are errors even in the MG Rover wiring diagram (which he won't have).

Simon

:eek: That's harsh, isn't it?

Everyone is free to do as they please irrespective of the advice that you may give.

I put up the link to Jules as I consider him to be the expert in these matters. :}

[SD1too]

Everyone is free to do as they please irrespective of the advice that you may give.
Agreed Neil. That's why I said this:
.. your wish to consult an auto electrician ... That's entirely your decision
So sorry, I don't see your point.
I put up the link to Jules as I consider him to be the expert in these matters.
That's fine, but again I don't understand what you're trying to say. :shrug:

Simon

[Richym]

The guys on here know more than all the autoelecticians i know. There help has been invaluable to me and helping me keep my 75 fit and healthy. I would always trust the member here and use there advise but as a last resort if all that fails is go to a trade and they will screw you out of every penny u have and probably not get to the bottome of it.

To me its sounds like u need a new fan from jules

[Neil1]

Agreed Neil. That's why I said this:

So sorry, I don't see your point.

That's fine, but again I don't understand what you're trying to say. :shrug:

Simon

This is what I didn't like;

I hope that you can understand that, having spent time giving advice, your wish to consult an auto electrician tends to suggest that you don't really trust us here in the club.What right do you have to say that?

Give advice freely but don't put a gun to someone's head over it.

David sent me a PM as he felt he couldn't ask any more questions without fear of being set upon for his decision.

In my reply I did say that an Auto Electrician may not be able to correctly diagnose the problem but then again maybe he will.
Neither of us know that.
I also said to ask Jules what he considers to be the problem.

[SD1too]

Neil; here is my perspective on the criticism you've made against me.
Give advice freely but don't put a gun to someone's head over it.
Why is asking someone to choose between consulting a business and an enthusiasts' club "putting a gun to someone's head"? That is a ridiculous suggestion. I explained to David why I would prefer him to make a choice, and since I am freely giving my advice I am entitled to make that condition. There have been threads where people in David's position have come to the forum for help whilst at the same time dealing with a trader. This puts those of us offering technical advice in a difficult position because, quite often, the OP will side with the trader because he's a "specialist" or the family have used the firm for years and trust him. In these circumstances the forum advisor has a lot to lose, and I don't want to enter into a protracted exchange involving a business. Sometimes OPs print out and pass advice given on the forum to traders. I don't expect the trader is too happy about that, and I sympathise with them in some respect.

Neil; please read all my replies to David and you'll see that I have already provided plenty of help in correcting some misconceptions he had. Despite this he repeatedly said that he was going to consult an auto electrician. If you were in my position, how do you think that would make you feel? That he believes what you are saying? :shrug:

David sent me a PM as he felt he couldn't ask any more questions without fear of being set upon for his decision.
If David wants to consult an auto electrician then why does he need to ask us more questions? He should ask the auto electrician, shouldn't he. Why is he making such a fuss about deciding where his loyalty lies? I suggest that he goes ahead with his appointment and if the electrician solves it then great! If he doesn't, David can always come back to us and there will be no conflict of interets then.

I also said to ask Jules what he considers to be the problem.
Yes, I know. I note that this is the second time you've said this to me Neil. Perhaps you are unaware that I have studied the 75/ZT fan system in depth for several years and consider it to be my "specialist subject". Other members do likewise: for example T-Cut in antifreeze chemistry and Stocktake with VIS actuators. If you think that Jules can do a better diagnostic job than I can, then that is your right. I am only sorry that I haven't convinced you that I do know something about electricity and 75/ZT fan systems.

Simon

[Neil1]

Hi Simon,

If you were in my position, how do you think that would make you feel? That he believes what you are saying?

It wouldn't bother me one bit.
Everyone is entitled to do as they please.

My specialist subject is electronics and fibre optics although I get lazy these days and tend to pay someone to do it for me.....;)

Neil :}