Always a good point. There is no heat with AC off, so I think it's OK, but I will check the valve to make sure it is closing.

 

Bill,
I had a heater valve that looked closed, bu still allow hot water to pass. The internal diaphragm was warped. Just an FYI...

 

Me too, but there was tell-tale heat all the time. In my case the center vent ran 10F over ambient due to the leak. I was told that's too small of a delta to be the heater valve, but when I replaced it, the center vent no longer was above ambient.

 

The weirdness continues....

Surprisingly, the AC worked fully today, blowing cold front and rear. OK, so expansion valve must have cleared itself.

Front blower suddenly stopped working. Rear AC blower worked, but no longer blowed cold. (Think that is expected in main blower stops).

Found front blower fuse 20 blown. Hmmm...found that a couple of weeks ago too. Replaced fuse. Checked blower cage and it appeared to move freely. Checked freeze switch plug and found 12V there. At pressure switch plug I saw only 0.5V. Checked back at freeze switch plug and it was then only 0.5V. OK, must be bad headunit. Maybe relay, but maybe not. Swapped in good headunit. Blower fuse blew immediately.

Replaced fuse, blower moved very, very slowly w/o AC switched on. We're done for the day. The car is hexed.

 

Sell it...

 

Usually when the blower keeps blowing its fuse means that it is getting old and is drawing too much current in order to run. Blower motor replacement time?

Dan
'91 928GT S/C

 

Bill the Rear AC is quite independant from the front - except of course that the compressor clutch is controlled from the front - if the blower alone fails that doesn't stop the rear - but if the front fuse blows or the relay (blower or AC clutch) fails the rear will not blow cold - as here.

If the fuse blows with a new headunit then it sounds like the blower or AC circuit after the relay - does the fuse blow with the blower on lowest speed - how about with the blower resistor pack connection unplugged (and blower switch not on high)

Next I'd unplug the AC circuit (Freeze switch) and see if its good then - maybe you have a short on the AC clutch feed - maybe that was causing your clutch dropouts?

Alan

 

Hi Alan: Thanks for the suggestions.

Thanks for indicating the rear is independent. When Konstantin brought the car back, I found fuse 20 blown and the compressor not getting a signal, so that would account for what happened right there. As I mentioned, I initially found 12V at the freeze switch, suggesting the relay is OK, but only 0.5V at the pressure switch plug. I confirmed wire continuity between the two. Still did not run, of course. Then found the freeze harness only getting 0.5V. So, that points to the headunit.

When I put the fuse back in for the front blower, it ran OK at first. After putting in the new headunit the fuse blew immediately in AC mode and on putting another fuse back in the fan only turned very slowly in non AC mode even on high speed, which is where we stopped. I'm going to remove the blower. Try again with the new headunit after I figure out what is going on with the blower. Resistor pack is new. I will check for short at the AC clutch too.

 

It's coming out for sure unless I can find a short in the circuit leading to it.

 

What does this freeze switch look like?

I replaced my expansion valve and have no clutch engagement when i jump the low refrigerant terminals. I dont recall seeing anything =, but i dont know what i am looking for. I did see something next to the AC resistor on the fan box. Its closer to the passenger side then the ac resistor but in the same general area.

 

Bill,

I had a similiar issue with my GT. The resistor was new but would only work on level 4. I was switching relays around for another issue and I replaced "Relay X" with a new one and that immediately fixed my blower problem and i got all fan speeds. I dont know if its coincidence or not but i thought i would mention it.