a/c blower issue
 

Hoping to get some guidance on an irritating intermittent cabin fan blower problem. 1995, 993 about 100,000 miles, new compressor seals, r/dryer, expansion valve, evaporator, condensor, and rear duct tube resistor 5 years ago. A/C functions in all modes, but sometimes the interior fans have a mind of their own. They suddenly operate at a speed not selected but always lower, maybe 1/4 or 1/3 of selected speed, but operate normally when the temp selector is selected full cold (blue dot). Pushing the upper fan switch (max cooling switch) does nothing when the fans are doing their thing operating at reduced default speed. Rear blower works, condensor cooling fan works, oil cooler fan works. I used to notice a "wheezing" behind the CCU
but this has now ceased. Pulled the blower fuse, it is fine. Any interior blower relays? ECU? CCU?

Is the little blower on the back of the CCU still working? Sometimes they fail ; that could be the wheezing you are talking about.

YOu have to pullout the CCU. Use some small nails inserted into the corners of the unit and it will pull out gently.

Cheers,

Mike

I'm also having a blower issue I think. Mine also does the fan speed "auto-adjust" to what it thinks it should be at I guess. I can drive it for a week, then one day it just does its own thing with the fan speed. I can get it to stop by adjusting the fan down a notch or two by the selector knob, but it will eventually do it again. This only seems to happen when its set to max AC by the push-knob next to the temperature selector.

any ideas? Parts of the AC were replaced after the car was hit and it had not done that before...

Thanks Mike, pulled the ccu, fan was inop, disassembled, cleaned, and greased needle bearings, works fine now, still no "wheezing" but we will see. Intermittent blower problem has become a daily issue now so we will see if this helped over the coming days.
Mark

I had a similar problem where the fan would intermittently cut out, only when the big snowflake was pushed in. I took the CCU apart, disassembled and cleaned the big snowflake switch, and all is well.

James, the Climate Control Unit is the panel where your temp selector, and fan speed knobs are housed. To remove, insert 4 nails in to the corner holes on the faceplate, (this releases the locking mechanism), reach under the dash push the back of the ccu forward towards you, move the wiper arm switch on steering column up all the way to clear the stock. Squeeze the release tabs on connectors on the back of CCU and pull out to remove the rectangular connectors, and viola!

Gosh, I don't know why. Mine just came right out after installing the nails. Maybe try, with one hand to push on the faceplate first (with the nails in) and with the other hand underneath the dash push on the back of the ccu. It may need to go into the dash a bit further before the locks release and you can push it out. Make sure the nails aren't too big (tight) then they might act like a wedge.

Today the intermittent blower fan continued to function briefly at a reduced speed, then went back to normal selected speed, so fixing the suction fan on the back of the ccu did not fix zee problem.

Reviving this old thread as I have been having similar issues with my car ('97 C2, ~88k miles). The AC blows cold when blowing, but the fan speed will step up/down by itself, and in some cases, stop blowing cold air altogether.

My first step is to remove, inspect and clean the CCU as described in this read. I also plan to go over Tore's pages for troubleshooting.

Other than that, has anyone had a similar experience and can share other things to check?

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Dave,

Use the snowflake left, bottom. only push that one in. Fan speed on high, main vents only.
Cold air? Speed stay constant?

Next, both snowflakes pushed in, fan speed on 1, vents on main.
Does speed and vents seem flaky? Speed up and slow down?

If all answers are yes, the most likely culprit is the contacts in the large snowflake switch needing cleaning. The large snowflake is trying to take control, and max cool everything. bad connection, so flaky results.

I guess you have a problem with the rear fan. The CCU will shut down the front blower fans periodically if it senses a problem in the rear fan.
Set the temperature knob to minimum, are the front main blowers working OK? If so, check rear fan: motor/fuse/low speed resistor/relay.
Cheers,
Tore

Many thanks techman. I ran the system with only the "small snowflake" button last evening, and had no issues over a 30+ minute drive. I'll clean the switch contacts and see if that does the trick before I start tearing apart the system.