johnRE

Can anybody help me please?

I have a 1991 Turbo 2. The rear heater blower fans are running continuously when the ignition is off. Pulling the fuses in the engine bay or in the front bonnet stop it, and the relays appear to be okay, has anybody got any ideas?

If anybody has had this problem can you tell me how you solved it?

Many thanks

Adrian

Dear John,
Pulling the fuse in the front (No 1) is a good clue. If you look in the plumbing of the turbo (I think the left side) you will see a fairly large connector in the plumbing. Remove this connector and the fans should stop. There is a sensor (a basic thermistor) installed in the plumbing which measures the air temp to protect against heat soak and engine overheating. This is called additional engine cooling. I suspect that this sensor has shorted out. Please remember that this is connector NOT the two spade terminals which are also installed into the plumbing which is a different component. You should check both rear blower fans. I cannot remember off the top of my head if there is one or two. I think only one but check anyway. The sensor sends its data to the ccu up front and then the ccu decides what to do. If less than 30C the ccu will switch off. If more than 30C the ccu will stay activated for 15 to 20 mins after the igntion is truned off. If the sensor detects 75C in this time it will crank up the fans at low speed. Because yours run immediately tells me either a shorted sensor or a ccu failure. I suspect the sensor as I said.
Ciao,
Adrian
964C4

johnRE

Dear Adrian,

Many thanks for the advice on fixing the heater which at last gives me a direction on this (it's been driving me mad!) and is greatly appreciated.

I will keep you posted on progress.



John.

maverick

Living in Texas it gets fairly hot in the Summer! I can't say that I have ever heard my rear fans staying on after I shut down. Is there a fuse for them? I do hear a fan when the car is running.
Maverick
'91 965 Turbo

johnRE

Still no luck with my rear heater fans.

Spent all Sunday trying to trace the fault, took the intercooler & air filter off to get to all the senders on the engine however the fans are still running (when the car is very cold they do not run but after running for 2 minutes they continue when the ignition is off) I guess as you said Adrian it must be a sendor unit because very small heat makes the fans run. I cannot find any sendor in the pipework for the turbo apart from the ones on the intercooler and the small resistors by the fans themselves. I have also pulled the sendor on the oil cooler radiator (front right) off but the fans still run.

The only other sendor I suspect might be a sendor (blue) by the oil pressure sender by the crankace breather pulling the plug off makes no difference but I wonder if I should connect the contacts together, could it be this?

I have also swapped a friends control unit but the fans still run and I am wondering if my car is haunted!

Any more ideas guys?


Many thanks


John.

andrew964

Don't suppose anybody has the 965 Turbo amendment for the 964 manuals?,
John's problem seems to be more one of, where are the sensors that control the fans and how do you test them,
having seen it in person it may well be a ghost causing the prob!!! but may just be something really silly and simple that were all missing

Thanks in Advance

Adrian

Dear John,
The rear blower fans for the Turbo are in each rear wheel arch. You have to go into the wheel arches, take the wheels off, remove the covers and check. I do not have the 964 Turbo maint manual supplements either.
Ciao,
Adrian
964C4