Trizza

New 1991 Carrera 2 widebody owner from Finland here! I'm currently working through some HVAC issues the car has, and would love some opinions.
I have been referring to https://www.bergvillfx.com/categorie...fault-overview and it has been very helpful so far.

First problem:
At first the front fans would shut off just after pressing the defrost button, or shortly after. After reading up on it I checked the rear fan resistor and noticed that it was partially dislodged from the pipe - I removed it, cleaned the contacts which were quite corroded, and replaced it. I also swapped the rear fan relay with the oil cooler fan relay. Now the rear & front fans seem to run properly - or at least they try to, before fuse #1 blows! If I slowly increase the fan speed with the temperature cold everything seems to work OK, until the fan setting gets a bit high and the fuse blows. If I press the defrost button while the fan is set to zero, the fans turn on briefly and then the fuse blows. If the system has warmed up a bit and the fans have been running for a while then press the defrost button then the fuse doesn't seem blow, at least not immediately, and the defroster seems to work as designed.

Any ideas? I have been getting some rattling/squeaking sounds when starting the fans up, so that all makes me think that the interior fan bearings are toast and trying to draw way too much current when they start or when they try to run at high load. I've ordered some non-OEM replacements for those. I've been having a hard time digging up information about how to go about replacing them - any links or tips would be much appreciated!

Second problem:
I'm getting white flakes/dust blowing out of the vents when the fans are on. For other brands of car I've read about this being related to the coating on the AC evaporator/condenser - could it be that? Or something else? Should it blow out eventually? Replacing that sounds like a major job..

Any advice is much appreciated!

ToreB

You can heck the rear fan low speed resistor with an ohmmeter. An OK resistor would read about 2-6 ohm, and if the thermofuse is relased you would not measure any value. This item is not very expensive and I recommend to change it to a new part to avoid problems.
One or both of your front blower motors are weared out. The bearings run dry and seize, causing excessive current, and the fuse blows. It is easy to remove the blower motor covers to check if they rotate freely.
Changing these motors is not straightforward, but covered in several threads here on the 964/993 forums.
The defrost flap has a foam covering that disintegrates. It is difficult to reach to the defrost flap without dismantling the complete airbox. The flap can possibly be seen through the centre dashboard vents, you maybe have to remove the vent .
Change fan motors:

• Detach metal clips on the lower edge and pull up/remove fan housing covers. Note their fitment along the edge before removal, they need to slide into the exact same position when reinserted. Have a magnetic tool ready to catch any clips falling down
• Remove the circular airstream covers inside the housing
• Rotate the fan cage to access, and remove the two Torx T10 screws holding the fan motor
• Use two long flat screwdrivers to depress plastic catches to be able to pull out motor from airbox seating
• Some use hacksaw blades to depress the catches, but a flat screwdriver is better. It can be fiddly to get the catches to release
• Right and left motor have different part numbers

Cheers,
Tore

Trizza

Thanks for the detailed post Tore! I'll give that a try. I found one other thread with what sounds like exactly the same fuse blowing issue, and it was the fans for him. I have new fans on the way so fingers crossed..

Trizza

The fans arrived late yesterday so I got stuck into the replacement - getting the old fan out proved to be quite tricky even after trying the hacksaw blade trick as well as using screwdrivers! It took me about an hour and a half to get access to the passenger side fan and then another hour to get the fan out. It felt like it span quite freely but I replaced it anyway. One of the spade connectors was quite loose so I wonder if that was causing some arcing issues. I tested after changing just the passenger side and the system worked perfectly! It's all back together now and I have a new driver's side fan for the future. The non-OEM fans are clearly quite a bit weaker than the originals.

Still no idea where the flakes are coming from - they're white/light grey, not black like the foam from the defroster flap.

heliolps2

Great job, Did you take pics? I think the white flakes you're seeing could dried condensation that loosened up when the fan got turned on after many years of not being used, That's what happed to me.Just a thought.
Enjoy

Trizza

I didn't take a whole lot of pictures, for the process I was mostly following the Pelican Parts article. That's for the 993 so the process was a little different, but mostly the same! I'm glad I didn't need to do the driver's side though as the AC pipes are in the way so you need to remove the expansion tank to get access.


You can see some flakes down near the evaporator here, looks a bit like white dust

I took the car out for a bit longer last night and the heater worked great the whole time It's just above freezing here at the moment so that defroster is essential! The previous owner barely drove the car the past 3 years and only in perfect weather so I think your theory about the flakes might be right - I see less of them every time I drive now.

chsu74

There is a good thread here if you search. The small screws anchoring the firewall is fiddly. Removing the fuel tank and vent hoses can be tough because its been locked in place for the past 30 years.

Passenger side has better access for sure. Driver side has two AC lines in the way but can be moved with a bit of persuasion without disconnecting.