rob0001

Checking my HVAC system with my piwis tester I got an error code 43 - Rear blower stage 1. Under drive links I can run the blower at high speed (stage 2) but at low speed (stage 1) I can only hear a humn/ buzzing noise like the blower got current but not turning. When turning the igniton key the rear blower runs always at high speed. The series resistor at the blower is new. Any ideas?

mgianzero

I know it's an old thread, but did you ever find out your problem? I have the same issue which I confirmed with a PIWIS 2 tester. My understanding is the rear blower will only turn on high when engine get too hot instead of low mode.

But would be nice to know if I should fix this. Could of sworn that I changed the series resistor a few years back at the blower. Could it have blown again? What's the test to confirm this? I forget - it's been years.

ToreB

Set CCU to max temperature and fan speed to 1. The rear fan shall then run on low speed. If it switches to high, the low speed resistor is most probably shot. The thermofuse on the resistor may be tripped. This might be possible to reset, but I always change the resistor when this happens.
The CCU turns on fan high if the fan does not run on low speed as a safety measure.
Use an ohmmeter on the low speed resistor. If it's a few ohms, it's OK. If it is open circuit, it is not.

The hum is probably not from the fan, but from the rear air selector vacuum valve.
Cheers,
Tore