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Test low speed fan operation for air con and oil cooler

Porker993

Porker993

New member
Just a quick question if I may

I have done the test mentioned in Maurice's excellent 993 technical article and found that while my oil cooler fan works perfectly, the air con fan only works at high speed. This confirmed my suspicion that something was wrong, as the aircon fan had begun "pulsing" on and off, instead of running continuously like it used to.

A simple question - how do I fix it ?
 
Maurice

So I have established that neither my low speed oil cooler or low speed a/c settings are working. I note your comments above regarding the low speed resistor. Is there a separate resistor for the oil cooler and how easy is that to fix? Also, is my car safe to drive if I keep on the move?
Thanks

Tim
 
Thanks Maurice

Having read the diy article again, I think I may leave it to the experts. Really grateful for your test as I could have been overheating my oil in blissful ignorance. I think I will resist the temptation to drive until it has been fixed.

Tim
 
Cheers Maurice - thanks for that. It doesn't really surprise me that the low speed resistor is stuffed if that is where it is located. I removed the washer bottle recently to fix the headlamp washer pump and in the process dumped a load of water on myself and everything else. For those who are unaware the washer bottle in a 993 is located thoughtfully just above the aircon condensor so everytime it leaks or overflows say hello to dodgy aircon electrics.

I'll get on to it as soon as this weather cools down a bit.
 
I have just replaced the oil cooler resistor (drivers side) and can confirm, whilst its fiddly and time consuming, its not difficult. I got to it by removing the leading wheel arch liner and the lower corner grill (undo all the self screws visible from below plus there's one between it and the bumper cover on the trailing edge in the wheel well and then the corner panel slides out forwards). I found I didn't need to remove the bumper cover. I had to drop the oil cooler itself, but that dangles by its own pipes once all the retaining nuts have been removed (two nuts on the rearward bracket, one on the leading edge, one on a support struct at the front and not forgetting there's one accessed from inside the headlight void, so you need to pull the headlight out as well). Its then posssible to see the resistor bolted to a horizontal panel above and to the front of where the cooler sits. The resistor nut is undone form below and I found there was just enough room to be able to unplug the connector and pull the resistor out rearwards from the wheel arch - actually mine came out in a handful of pieces. The new resistor is supplied with a steel washer to seat it on so I lightly taped this to the resistor with electrical tape to hold it in place while I threaded it back into position. Happily everything went back together without leaving any left over nuts! Oh, and I also put copperslip on each of the liner screws to make their removal easier in the future - most were fairly corroded and difficult to undo. About 3 hours in total.
 
The reason I asked is that my air con now pours out hot air and only starts to get cold when I turn it right down, so not getting any control over temp Either too hot or too cold!
 
Tried it this morning and when the aircon is on with no blower, can hear a whirring noise which then stops. Some of the Rennlist guys reckon that it may have something to do with the flaps in the footwell or the luggage area.
 
I have not had time to start fiddling around looking to see if the flaps are working and it is also too cold at nights, even in the garage!

Was hoping it was something simple like the relays, but it never is that easy!!!!!

Once I get a bit of time will have a poke around and report back.
 
Just to add my bit.

When the weather was a little warmer, back in September, I changed the A/C resistor myself. I actually removed the whole front bumper(PU) as I was told this was the ony way to reach the resistor. I also dropped the radiator a little and this could not be done without removing the front bumper, there is one hidden nut. Isn't that always the case! Anyway all went OK and in the end did not take that long.

On later consideration, I think it would be just possible to change the resistor without removing the PU if you have the right tools. As Maurice suggests you need a 4mm allen key type of tool attached to a small ratchet tool, I am not sure of the exact technical name. Even with this I think it would be very fiddly, but worth a try as it would save much time.

Although I have done a lot of car DIY jobs in the past, I only really had the courage to tackle this job having watched it done by Jez Parsons of Carrera Performance at the Porsche Festival.

Michael
 
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