bricem13

Hi

Got a drive today. When i parked i did a test: stop engine - no rear fan on, turn ignition on - rear fan at full speed and then after a while low speed and then off.

I know there a kind of cooling function of the rear fan when it gets hot but why does this dawn thing works only with ignition on? Or do i have an issue here?

Thanks

Spokes

Connect a scan tool or PDT999 etc to read faults. You may have a faulty rear blower resistor or air temperature sensor for blower.

freno a mano

Mine does the same.

John McM

cjoenck

So my fan behaves the same way. Engine is very hot after stop and go traffic, oil temp between 9:00 and 10:00 and front oil cooler fan is running. Rear fan is supposed to move heat away from engine when engine is stopped. So why does the fan run only with ignition on and stops when ignition is off? I understand the fan is controlled by CCU but how is a mystery right now.

ToreB

The rear fan will only run in engine cooling mode if no heated air is needed to the cabin. This depends on the temperature setting and the ambient temperature. No heat is needed to the cabin at ignition off, the rear fan will therefore start in cooling mode if it is sufficient hot back there.
Be sure to check if the rear fan runs in both speeds.
Here's how:
Set to max temp and minimum fan speed.
The rear fan shall run in low speed.
Set fan speed 2 or more, rear fan shall run in high speed.

If the fan does nor run in low speed, you most probably have a defective low speed resistor or fan relay.
The CCU supervises the rear fan, and will default to high speed if the resistor is dead.
Cheers,
Tore

JasonAndreas

The functionality was added during MY91

.

bricem13

Lots of replies thank you guys.

I am confused with last reply as temps are 95 and 93 degC whereas ToreB website mentions 75 and 70 degC as thresholds.

Also no mention of it being from MY91.

It might be interesting to have details of the temp sensor to try to shunt it to check functionality.

I wonder what would be needed to get it for a car before MY91.

Best regards

JasonAndreas

The temperature threshold was lowered for the 993 version of the CCU.

midnight 911

Test by un-plugging air temp sensor after ignition off.
If I un-plug the air temp sensor with ignition off, my rear fan runs. I assume this is for 20min after ignition off.
I have never noticed mine run in the garage after hot drives in Australian summer. (maybe i should check resistance of my sensor...)
Mine is MY91.