porsche 996 engine purge fan turns on too often

[mffarrell]

I have noticed that the engine blower fan started to turn on right after I added an aero wing. It will come on on a cold day after the engine is warm, and will cycle, especially at lower speed driving.

The engine temperature is normal, and there are no warning lights. I checked the sensor to make sure it was seated correctly.

If there anything else I should check before replacing the temp sensor?

Thanks!

[Ahsai]

Are you sure it's not the secondary injection pump you are hearing? My sec inj pump turns on for 10 seconds or so sometimes when in stop and go traffic.

[JFP in PA]

Are you sure it's not the secondary injection pump you are hearing? My sec inj pump turns on for 10 seconds or so sometimes when in stop and go traffic.

I'm not sure it should do that, it is supposed to only run at start up to aid cold start emissions...........

Edited December 10, 2012 by JFP in PA

[mffarrell]

Are you sure it's not the secondary injection pump you are hearing? My sec inj pump turns on for 10 seconds or so sometimes when in stop and go traffic.

No, it's definitely engine purge fan, as I can see the fan blades turning.

[Ahsai]

Are you sure it's not the secondary injection pump you are hearing? My sec inj pump turns on for 10 seconds or so sometimes when in stop and go traffic.

I'm not sure it should do that, it is supposed to only run at start up to aid cold start emissions...........

Yea, that's what I thought too until I saw a document (most likely in renntech) saying there other non start-up conditions that it will run as well. I can't locate the document now though...

[Loren]

The aerokit wing uses a different wiring harness - did you use the one for the aerokit?

[mffarrell]

The aerokit wing uses a different wiring harness - did you use the one for the aerokit?

Loren,

Yes, I used the harness that came with the aero wing. The wing was from a MY 2001 with a factory installed aero kit. My car is a MY 2003. My understanding is that the fan is switched on when the engine compartment temperature is > 176 degrees F or the coolant temperature is > 216 degrees F.

It appears that the ecu is activating the fan based up on the above criteria. Is there anything else besides the temp sensor that would give the ecu incorrect data?

Do you have any ideas how to troubleshoot this issue?

Thanks!

[Loren]

Not really - in most cases where the fan is running too often it is because the sensor is lying on the hot engine instead of being suspended in it's holder.

Could be a bad sensor. I am not sure of the resistance of a good sensor - perhaps you can borrow one to test and compare.

[mffarrell]

Not really - in most cases where the fan is running too often it is because the sensor is lying on the hot engine instead of being suspended in it's holder.

Could be a bad sensor. I am not sure of the resistance of a good sensor - perhaps you can borrow one to test and compare.

I checked the sensor, and it is mounted securely. I wonder if the harness could cause this problem? I wouldn't think so b/c the power to the fan is supplied by a relay through the harness to the + and - terminals on the fan. The fan turns on and off.

I think I have a measurement problem, as the temp sensor could be providing the wrong resistance to the ecu. I am not sure what else it could be.

Thanks!

[flxzcat]

The wing might be drawing more hot air past the sensor and local sheet metal thereby raising the temp in heat soak?

Just a thought...I don't even know where the sensor is located.

Paul

[mffarrell]

The wing might be drawing more hot air past the sensor and local sheet metal thereby raising the temp in heat soak?

Just a thought...I don't even know where the sensor is located.

Paul

Sensor is located on top right bank .