skl2

I just replaced the blower motor relay because I wondered if that was the culprit, but it appears that it is not. The blower continues to go on and off with the ignition. I just took it out and checked the wiring, and everything appeared fine. I replaced the relay, but it didnt help - if the ignition is on, the fan is on.

Just to make sure I wasn't going crazy, I double checked it on my friends 993 and his operates as it should....mine is def acting up.

Anyone have any thoughts?

Rutger Gert-Jan

Did you replace the relay in the engine compartment? (i think you did, just to be sure) Otherwise have a look at the temp. sensor in the black plastic or rubber pipe leading away from the blower.

Neil Perry

Hi
If you check your operational book the blower switches on and off up to 20 minutes from switch off.
This is normal operation.

But the fan does not go on and off with the ignition switch, there could be a sensor fault.

Although good start replacing the relay.

Need to check if there is a separate sensor for the fan

skl2

I should have said I also checked the temp sensor and it was working properly. I simply did this by swapping it with one from my friends car because his is operating normally.

I know the blower can go on and off after shut down, but my car has been sitting for 3 days and every time I turn the ignition on, it starts blowing.

techman1

I think it is also tied to the temp of the selector for the cabin ac. If it is full hot the blower will come on. Or something like that. Just keep in mind the AC CCU switches it on.

skl2

Yeah, I wondered about that and played with the temp selector with the ignition on to see if there was a change in the blower....nothing seemed to change the fact that it goes on with they key. I might remove the CCU and see if that causes any changes.

EMBPilot

it is... to stop the blower from coming on with the ignition switch turned to ON, keep the temp controller turned full counter clockwise. once you start to move it up past full cold, the car will run the fan.

techman1

Kent,

When at full cold does the fan still run?

skl2

EMB and techman, I will double check this as soon as I get home and report back.

Thanks.

Mike J

By temp sensor you mean the coiled wire sensor in the tube that runs close to the distributor? If that one is unplugged or faulty, it can cause the fan to run continuously.

skl2

Hmm, no, I was actually referring to the one a little above that. it has an electrical connector clicked on to it.

I did check the connection to the coiled sensor and all appeared ok, but I didnt think to swap that out and see if it was the root cause..... I will put that on the list.

ToreB

The rear AUX fan has two purposes. One is to help blowing air through the heat exchangers onward to the front fans to improve the heating of the cabin. The second is to do additional cooling of the heat exchangers/engine when in normal operation, and at ignition off by blowing the heated air out through two spring loaded dump valves under the engine. The Climate Control Unit controls the operation of the fan.
The temperature sensor for the AUX fan is placed on the big air duct, and have a electric connector on it as skl2 mentions. There's also a ballast resistor to enable low speed on the fan when it helps pushing air to the cabin, and this resistor is placed in the same air duct below and to the left. It's a open wire-wound resistor, but also has a bimetallic switch that will shut off the current if the fan motor seizes or draws abnormal current to avoid overheating of the resistor and possible fire. The fan runs at full speed only when in cooling operation, so the resistor is not the culprit here.

I've seen several cases of the fan running in cooling mode after ignition off until the battery goes flat, I would think this is due to a defective temp sensor, wiring (corrosion in a connector)or relay fault. I have also experienced abnormal long running times after being out in wet weather, but have never been able to find the fault.
Check the temp sensor connector for corrosion. Test the sensor with an ohmmeter, you should read about 12,5kOhm at 20degC and 4,4kOhm at 45degC.
Almost all details on this are given on my HVAC DIY page.
Cheers,
Tore
Here's the temp sensor(4.2) and resistor4.1)

BesideTheBox

Skl2 - Any update?

Does your rear AUX fan go off when you turn the temperature to minimum (all the way counterclockwise)?

Does your rear AUX fan go off when you select reverse?

Car does not need to be running to test this - just turn the key 2 clicks.

Because it is cold here in MN and my garage is not heated, my rear fan runs at any temperature selection
above minimum. At least I think that is the reason. Your original post was in December and your location
shows IA, so maybe the cool ambient temperature is the reason for the fan running.

skl2

sorry for the delay...Im not on the forum quite as much now that I am 993-less.

Issue turned out to be very simple: I had moved the climate **** and didnt realize it. As soon as I turned it all the way down, it went off.