Cascade Crew

fiveoformula · Posted: Mon Jul 07, 2014 9:53 am Post subject: HVAC issue

So after I replaced my leaking heater core last month, a day or two later I noticed I only get air flow from the a/c or heat blowing out the defroster at the windshield.

Im guessing I bumped something while installing the heater core. any thoughts?
Have not pulled anything back apart yet.

iansane · Posted: Mon Jul 07, 2014 10:34 am Post subject:

The whole HVAC setup gets vacuum from one small hose through the firewall right around where the heater core lines go through. Did you bump off the source hose? It's a hard plastic line from the firewal meeting a regular hose connected to the engine. There should be two down there. One for the heater control valve (if you still have that?) and the HVAC vacuum source

Xophertony · Posted: Mon Jul 07, 2014 11:31 am Post subject:

I did this in my GTA about 4 years ago. The heater never worked right again until I pulled the vacuum operated box in favor of a cable operated non-ac unit. If I ever put A/C back in the car I will run those vacuum lines through a different firewall location. Fixing those lines may require you to pull your dash.

fiveoformula · Posted: Mon Jul 07, 2014 11:38 am Post subject:

I could have easily bumped that hose. the core was a pain to get out. I don't have a heater valve anymore and that line I just have capped off and hidden.
So this one vacuum line, is it just to the left (drivers side) of heater core?

aaron_sK · Posted: Mon Jul 07, 2014 11:52 am Post subject:

The black feeder line turns purple shortly after it comes through the firewall, and ends up at the selector dial on the HVAC control.

No way to determine where the failure in the line is without putting eyes on it and finding the break. I would pull the dash pad off and shine a light down there to see if you can see the purple line.

fiveoformula · Posted: Mon Jul 07, 2014 12:24 pm Post subject:

It seems this car really doesn't like me turning on the A/C. The compressor really whines and idles rough with it on. Need to check that vacuum line so it doesn't just point at the windshield.

aaron_sK · Posted: Mon Jul 07, 2014 12:52 pm Post subject:

Sounds like the compressor itself might be failing.

Is the system charged? Was it run for a long time without freon?

fiveoformula · Posted: Mon Jul 07, 2014 2:00 pm Post subject:

Not that I aware of. Years ago I converted it to 134A. Doesn't seem to leak because its been years since the conversion and it still blows cold air.
Just noisey when its on.

Twilightoptics · Posted: Mon Jul 07, 2014 4:00 pm Post subject:

Could be belt, could be clutch, etc for the squeak.

Like the others said, you have vacuum leak now - defrost air only and engine pissed off.

83Z28BlackBetty · Posted: Fri Jul 18, 2014 2:28 pm Post subject:

Defrost is the default position for the HVAC ducts. So if there is a lack of vacuum it will be stuck on defrost. +1 for checking the vacuum hard line incoming.
~JAKE

fiveoformula · Posted: Mon Jul 21, 2014 8:18 am Post subject:

I havent gotten around to checking it yet, but engine definitely freaks out when I switch to A/C. That must be it.