Tech Area > General Buick Tech
Heater valve vacuum problem
LeeRoy:
Hi,
My heater valve is opening during boost and even light driving affecting my AC air. I'm sure it's the valve as I bypassed the heater core and I get cold AC all the time.
I assume a bad or missing check valve or something else?
There is 1 check valve on the drivers side going to the metal vac line. That one is ok.
Are there others?
Any tips on how to troubleshoot?
Also, when I turn the car off the heater valve maintains a vacuum source for hours.
Thanks
Steve Wood:
The vacuum line that goes to the firewall should have a small check valve in it to prevent boost from blowing into the AC controls and also to the vacuum storage ball that is under the fender just in front of the drivers side front tire...you can see the ball if you are laying on the ground and looking up just in front of the tire.
Now the line that runs to the firewall connects to a vacuum distribution valve and that valve also has check valves built into it. One side of this valve goes to the reservoir ball and the other side is connected to two small hard plastic lines-one goes to the heater valve in the heater hose and the other small line goes into the car to the ac controls.
You can check the small check valves by blowing into them from the vacuum block side or where the metal lines come out. You should not be able to blow thru them but you should be able to suck thru them. This prevents boost from going to the AC, heater, and cruise control. If the distribution valve on the firewall is bad, it will fail to provide vacuum to the various controls that need vacuum to operate.
Right now it sounds one of the small check valves is probably bad or missing. They are available from the parts stores.
Steve Wood:
The one on the firewall should be this one https://www.oreillyauto.com/detail/c/dorman-help/dorman-help-3-16-3-16-1-4-inch-wye-y-check-valve/mtm0/47150/v/a/2665/automotive-car-1986-buick-regal?q=2+way+vacuum+check+valve&pos=0
the line on the bottom goes back to a vacuum line coming from egr vacuum line area as I recall. The one to the right goes to the cruise control and vacuum storage ball and the top one goes to the AC controls.
As I said, I suspect it is one of the small two way check valves in the line rather than this one, but, I have found it's a good idea to replace them all as most of them started to fail 20 years ago from age.
LeeRoy:
Thank you. Will check.
Just a Six?:
Steve so glad I checked this post as for years I've had weird issues with my ac on Hot days & I don't think I have any check valves in my lines. I always knew that's why my cruise control doesn't work but this explains the other issues my ac gets on hot days. Time to find a couple check valves again. Years back I picked up a half dozen but they are MIA & now that I moved last fall all my stuff is in boxes in the garage so no chance I have them anymore. I'll look for that one you posted up out here in the Great White North!
Thanks you're always a wealth of info to all of us! :rock:
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