Peter65

When I bought my '96 993 late 2022, it turned out that the airco didn't get very cold. The problem appeared to be a leaky condenser unit and I decided to leave it as it was and to just enjoy the new to me 993 for the first season, as I live in a moderate climate anyway. All other ventilation functions (heater, fan) worked just fine, so I just dealt with hot days by opening the sunroof or the windows. Recently I decided to take it to my specialist to swap the faulty condenser unit for a new one, because I like the car to be 100%. They did a good job and everything looked to be working fine with the a/c getting cold as it should while testing (the car running at idle in the workshop).

However, during the first trip I switched on the a/c and while the fan started blowing, the whole system fell dead within 2 seconds. It had blown fuse #1, which leaves you with no ventilation functions at all. Once home, I replaced the blown fuse and everything worked fine again when running at idle on my driveway. But yesterday, on my first trip with the car since then, I switched on the a/c while driving and it blew the same fuse again almost immediately.

Due to practical reasons, it will take a while before I can get back to my specialist (who is absolutely helpful). Meanwhile, anyone has an idea what the source of this problem could be?

ToreB

Fuse 1 powers the CCU as well as the two main cabin blower motors. These have sintered bronze bearings that wear out, and the axle will not rotate freely when the bearings get hot. This causes excessive current and blows the fuse.
Remove the pollen filter covers and rotate the blower cage to find the one with problems.
Changing the motors is a bit fiddly, there's several threads on this topic here on the forum.
Cheers,
Tore

Peter65

Thanks for your reaction Tore. This sounds like a reasonable cause for the problem.
However, the cabin blowers (didn't know there were two of them) seem to work without any problems at maximum speed when the a/c is switched off. Or is there something I'm just not getting?

ToreB

Still: Fuse 1 blows = bad fan motor(s) No other items involved in the HVAC can produce a current larger than 30A without generating smoke.
Maybe you did the test when the fans had run for a long period, giving the worn-out bearings time to go hot and squeeze the rotor axles. A sudden transition to max speed could then blow the fuse.
Cheers
Tore

Peter65

Thanks again, I will have a look at it and keep you posted!

pp000830

Consider a drop of light oil on the cabin blower shafts where they meet the blower housing. Some will wick into the bushing and may forestall replacement, possibly for quite a while.

ToreB

Many have tried this, resulting in a burnt oil odor in the cabin until the fan motor seizes again. You will not be able to reach to the rearmost bearing of the motor without dismantling it from its recess in the air box. If you have come this far, you can change the motor anyway.
Cheers,
Tore

Peter65

You were right, Tore! Both fan motors are on the way out. When tested seperately on full blast, the right hand motor blows the fuse in seconds, the left one takes a little longer but will eventually blow the fuse just as well. Two new fan motors have been ordered, so now only the fiddly part remains.

Peter65

Replaced the two fan motors today and the problem seems to be solved. No problems with the ventilation at full blast, no matter whether the a/c switched on or off. And with the a/c switched on, it gets perfectly cold. Thanks for your support, initially I wouldn't have suspected the fan motors themselves.