[perbal]

After using my A/C for the first time this year last week, I tried to use the cabin blower fan for fresh air and found that it was not working on the first three settings, but works on the high setting. Check fuses but didn't spot any needing replacement. Any ideas? Thanks.

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[PorscheDude]

There is a big resistor pack for the blower motor that needs to be replaced.
I think I might have one if you need it. I think (can't remember) the resistor pack is mounted to the firewall behind the glove box.

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[Kim]

The reason which the first three speeds don't work is that the resistor cuts the power in stages to reduce the speed. When the resister is bypassed (speed 4) the fan just runs directly on full voltage- doesn't matter if the resistor has failed or not.

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[prj24149]

Resister pack is screwed to the top of the fan housing, under the plastic cover next to the firewall.
Interestingly, my 0-3 positions work but the high 4 doesn't. Can't explain that one. Any ideas?

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[Kim]

Clearly, it must be the reverse of the other scenario. What other possible explanation is there?

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[rxter]

Another related, yet completely dissimilar question. The horizontal slide bar. I presume that is supposed to modulate the flow of air like an open or closed switch. Slide the top one to the right and you have more air from your dash vents (assuming that you have moved the vertical slide bar down away from the defrost setting). The bottom slider (foot area) seems to work OK, but the top one seems to do nothing. Not super annoying, but it perplexes me. I don't know if its broken or just a really poor design.

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[Kim]

The top one moved to defrost only works if the vertical one above it is moved up. Germans did not want us to have defrost unless we truly desired it.

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[jfrahm]

In the fan speed resistor module there is an overtemp switch that can get dirty. There are two of these on a 944 but I think only one on a 968. This gadget is on the LH side (LHD driver's side) in the air intake for the HVAC system. The overtemp switch looks like a small reed switch or relay.

I have cleaned these little guys with some paper and a drop of acid, followed by a good bath. It's important to get the contacts apart so the inner surface gets cleaned.

I have also had my fan control switch in the Climate Control head break to cause this same problem of only high-speed fan. I replaced my fan switch with one from a scrap CC head. If you decide to replace, the 968 and 944 CC heads from 87 or 88 are much improved, much smaller, more integrated electronics than the 85.5-86 ones (not sure about the dates.) All I know are some of the scrap ones I got were super bulky and stone-age looking.

The 968 also uses a detent pot for the temp control, so if you grab a late 944 CC head that might not be the same.

Cheers,
-Joel.

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[jfrahm]

"There is a big resistor pack for the blower motor that needs to be replaced.
I think I might have one if you need it. I think (can't remember) the resistor pack is mounted to the firewall behind the glove box."

That's the resistor pack for the radiator fan. The big ceramic pucks. the AC blower pack is on the other side.

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[durtkillon]

I love this forum. It saves me sooo much time troubleshooting.



I just ran in to this problem this week. The fan would work only if it was set to 4 on the control. I took the series resistor off and noticed the insulation on the resistior coils was gone. That shouldn't matter, so I ohm'd the resistor and there was no interruption - it seemed to be doing it's job. I thought I was stumped, but when I put it back together, the fan worked fine. I then proceeded to clean up the contacts with my trusty Radio Shack contact cleaner and put it back together. I'm pretty sure I just had some corrosion in the contacts.



By the way, the part number is 944.616.105.00 and Porsche refers to it as a "series resistor". It retails for about $80.



I replaced the cabin filters while I was in there. Yuck! That was long overdue.

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