Rear blower motor on high speed

[acme]

I've been reading around on this topic and am still confused, some assistance/advice would be appreciated Gents.

Upon turning the car on to ignition position 2, but not firing the rear blower comes on at maximum speed, & I'm sure it didn't use to be like this. The car hasn't been fired since the end of October, so needless to say is cold.

Having read up etc I thought it was the resistor, tried cleaning the contacts and no change so bought a new one. However, I've installed that and still no change.

Fan speed is on no.1, temperature is above 16 i.e. not at minimum. When I do turn it to minimum the blower turns off, I assume this implies the CCU is working?

I note including on Tore's site that there's mention of a thermoswitch I believe on the resistor itself and that you can reset it, any ideas how?

In short, do your blower motors turn on at full speed prior to firing, and if not any ideas how to resolve mine?

Many thanks in advance for any help.

 

[ToreB]

If low speed does not work, the CCU will default to running the fan at high speed.
If the resistor is OK, you have to check the rear fan relay, this wears out. The same type of relay is used on the oil cooler and condenser fans.

The CCU will also default to high speed if the rear air duct temp sensor is either disconnected or defective. A Porsche compatible tool will be helpful to see if this is the case, but manual ohmmeter measurements can also be done on the CCU harness connectors.
Cheers,
Tore

 

[jonttt]

My journal may also help

http://911uk.com/viewtopic.php?t=82158&postdays=0&postorder=asc&start=403

 

[acme]

If low speed does not work, the CCU will default to running the fan at high speed.
If the resistor is OK, you have to check the rear fan relay, this wears out. The same type of relay is used on the oil cooler and condenser fans.

The CCU will also default to high speed if the rear air duct temp sensor is either disconnected or defective. A Porsche compatible tool will be helpful to see if this is the case, but manual ohmmeter measurements can also be done on the CCU harness connectors.
Cheers,
Tore

Fantastic, thank you Tore :thumb:

As suggested I swapped the oil cooler relay over for the blower motor in the rear panel & it now works as it should; low speed on position 1, high on 2 or above.

Now to get a new relay.

For anyone reading this thread in future, test the relay before buying a new resistor, £50 saved.

 

[acme]

My journal may also help

http://911uk.com/viewtopic.php?t=82158&postdays=0&postorder=asc&start=403

Many thanks for your reply.