| Need help with cabin heat ASAP (solved for now) [message #340665] |
Tue, 05 February 2019 22:48  |
NextGenGMC
Messages: 146
Registered: December 2017
Location: Washington State
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Senior Member |
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Hello fellow GMC'rs,
I need help and I need advice regarding cabin heat. I have a trip coming up in a few days. The temps outside have dropped, not like in the mid-west but still cold, and my cabin heat stopped working. I had some issues with it before, but I thought I had it solved with re-connecting all the vacuum lines on the controller unit.
Right now I have the fan blowing, but not getting any heat at all - just cold air. I found out that my vacuum valve on the line to the heater core was not operating (not getting any vacuum). I put a zip-tie on it to keep it in fully open position. This allowed fluid flow and it actually produced heat in the cabin but only to the center outlet. Also, when controls were in the DEFROST position, I was also getting warm air delivered to the windshield. That sounds great and I though I had the issue solved... Unfortunately, after playing with controls some more, the heat stopped completely. The valve is still in OPEN position, the heater blend door seem to be in proper position for heat (lever position on the box does change when I switch from COLD to HOT). I do have vacuum feed to the vacuum canister (about -16-17 in Hg) and out of the canister and to the controller in the cab (about -15 in Hg). I'm getting vacuum to some of the selector valves (center one on defrost and the one on the passenger side for sure).
What am I missing and what can be causing the lack of heat?
One thing that puzzles me is this: the rubber hose going to the heater box warm past the vacuum valve (not hot, just warm). However, return hose coming out of the box is ice cold. If I touch the same outlet hose further down, closer to the radiator, - it is as warm as the Input hose. Could my heater core be completely plugged and not allowing coolant circulation at all? What else do I need to look for?
Any advice is appreciated. For this trip I might have to bundle up in blankets  but still need to get this solved eventually. Especially because I can tolerate cold temps much better than my significant other 
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
[Updated on: Wed, 06 February 2019 11:09] Report message to a moderator |
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