Dreaded HVAC problem returns

Time to troubleshoot the vacuum system again for the HVAC. I have checked the engine with the mighty-vac following Wally's advice and the heater valve is new last year (although could have failed of course).

The symptom is warm air all the time, but occasionally the cold will kick on fully and work a few minutes, then go away again. I found a check valve in the wrong place in the engine bay but that did not resolve it.

I have replaced all the internal vacuum manifold solenoids last year, but I will go through those with the mighty-vac as well. But I am thinking it may now be a setting motor or a bad temp sensor circuit or maybe a bad vac line.

Wish me luck! Will let you all know how it goes.

Strat_928;9206 wrote: Time to troubleshoot the vacuum system again for the HVAC. I have checked the engine with the mighty-vac following Wally's advice and the heater valve is new last year (although could have failed of course).

The symptom is warm air all the time, but occasionally the cold will kick on fully and work a few minutes, then go away again. I found a check valve in the wrong place in the engine bay but that did not resolve it.

I have replaced all the internal vacuum manifold solenoids last year, but I will go through those with the mighty-vac as well. But I am thinking it may now be a setting motor or a bad temp sensor circuit or maybe a bad vac line.

Wish me luck! Will let you all know how it goes.

Good luck, I haven't gone there yet

Trust me - you don't want to.... I think it is something that will just nag until I get a lot of old rubber line and bad flaps etc. replaced,,,unfortunately the ones on the inside are bears to deal with. Even then it may haunt for a while.

To start I may wire the heater valve shut to prevent Hot h2o from entering the tank. It is a quick fix while I take time to troubleshoot. Even then, I may wait until I get the dash out to get the interior done....do it all at once. Until then I will have A/C for the sweltering Va summer....and the trip to NC for SITM on I-81. Will keep you posted.

Strat_928;9234 wrote: Trust me - you don't want to.... I think it is something that will just nag until I get a lot of old rubber line and bad flaps etc. replaced,,,unfortunately the ones on the inside are bears to deal with. Even then it may haunt for a while.

To start I may wire the heater valve shut to prevent Hot h2o from entering the tank. It is a quick fix while I take time to troubleshoot. Even then, I may wait until I get the dash out to get the interior done....do it all at once. Until then I will have A/C for the sweltering Va summer....and the trip to NC for SITM on I-81. Will keep you posted.

I bought some of that cool orange, blue and red and gray silicon line and is it ever sweet.

I put a manual valve in my heater line. I block it in the summer and open it in the winter works great. I got tired of not knowing if it was going to work or not! Too hot in Louisiana not to have a/c blowing 100%.

Hey - great minds think alike! That is exactly what I ended up doing today.

Went to Napa and bought the BK 6601413 (3/4" hose), all metal manual heater valve. It fit in line as a direct swap with the normal heater valve I took out. Just capped the Vac line going to the inside. Didn't not lose too much H20 either just plugged the ends with rags during the work.

Went for a drive and voila! A/C or Fresh Air,,,,either or! Since I have owned it I have never experienced such normalcy in the HVAC. I am ecstatic

Taking off the air cleaner itself is probably harder, so it is not a big deal to do the swap. I heard some people put it inline along with the regular valve against the firewall, but that looked really to hard to get to and cutting that hose made me VERY nervous. So it works great as-is and is just an hour job or so now that I have everything.

I am keeping the regular valve to put back for winter. The reason is because it does seem to allow some temperature variation for heat. For Summer, all cool 100% is no big deal, I can switch to a lower fan speed. In Va, when it is really hot, you need 100% cool. And when it is nice, the sunroof and fresh air is plenty.

Total cost - $20.00. Best bang for the buck you can do most likely if you are having all hot issues. it also showed that most of the rest of the system was in pretty good shape since I have get fresh air or Econ and defrost along with A/C whenever needed. I was getting hot all the time, now everything works, (except heat of course) even out of the door vents which were especially hot, and all I did was cut the hot water off.

I tested the old valve a little. It is actually only a year old, the replacement plastic one. But I filled the end with water and it would drip a little, so it was likely leaking even when closed. It would hold a vacuum. But now I can be sure hot water is not getting in....AWESOME.