JKW993

nile13

Try the following: set the temperature control on full heat and fan to position 4. Report the results. Also, press teh Max Air button. Report the results.

Pedro356C

Have you got a squeaking sound from the fan at lower speeds? If so, your fan's engine is almost done and you'll have to replace it...I replaced mine a couple of months ago...

fbfisher

I was recently told that the pollen filters, when very dirty, will reduce air flow. That was the answer to the question: "why do I need pollen filters on a cab - seems like a waste of money?"

nile13

JW, you should contact Randall G if he's still around, he's the HVAC God.

But basically, I would check the relay thats' responsible for the engine compartment fan. Here's my post from back a year or so ago:

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Randall, as usual, was right!

My lack of high speeds on heater fan was due to bad rear blower relay in the engine compartment. Replacing it with a good relay gave me higher and highest airflow on positions 3 and 4 of the blower controller. I'm still not sure that positions 1 and 2 give different flow, but that's a very secondary issue. As I had problems with windshield fogging several times before, I am very greatful for this solution.
The relay is a VW-Audi part, 811 951 253 (it also says 89 82 99 on it). I need to cross-reference that to Porsche # or better yet stop by at a VW dealer that is 5 minutes away and get a replacement. I will also try to re-solder the contacts on the bad relay today just to see if that wakes it up, more a curiosity than anything else.

So, once again, my thanks to Randall.G, a true guru of HVAC!

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Here's the thread you need with all the details: https://rennlist.com/forums/showthre...77#post1078577

jnor10

I would summise thats its either the ECU,a vacuum leak to the back of the ECU or somewhere else in the system or the heater valve controllers that are located in each footwell.

You might try the controllers in the footwell first, check the vacuum connection on the back of the ECU and verify its connected. Lastly try to swap out ECU's if you have someone in the area that has a 993 or 964?.

From your checks so far,it appears the fan is not at fault.

Good Luck

Jeff N.

farmerjohn

If someone's been working in the engine bay, make sure that they plugged the blower fan wiring connector back up. I had a similar problem; resolved when I plugged the blower back in.

Carrera Mike

JKW993,

There's like a screened hole, about the size of a quater, I believe to the left of the controller(Left of the left ****). Inside it is the temp probe/sensor. Pull it out(If I remember right, when I worked on mine, I have to pull the whole face plate of the A/C), I bet you that the probe is 'caked up'/covered with dust and its having a hard time detecting the temp in your cabin and messing up the computer to properly run the fan speeds.



This is one of lister's dash.