vacuum leak in heater/ac control
02-28-2004, 06:24 PM
#1
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vacuum leak in heater/ac control
I've had this leak for a while, but lacked the motivation to investigate it until I had the center console apart for another project, anyway.
Looking at how the upper and lower ac control valves fit together, I don't see how there couldn't be a leak there. The pieces do not fit tightly together. There is a sizable gap between the three pieces (upper and lower valves, and the plastic disk with pivot arm on it that goes in the middle).
Wombvette mentioned replacing a plastic pivot rivet that generally breaks, causing a leak. I didn't appear to have any rivets that were broken, it just isn't a tight fit. Is it supposed to be a tight fit? Is the lack of a tight fit causing the leak, or is something else the cause? I guess that I don't quite understand how this valve works.
Also, my heater blower switch has problems. It doesn't change speeds as you change positions on the switch. It will go into high mode, but only if you push the switch all the way forward, then bring it back a half detent. Is this indicative of a faulty switch?
Thanks for any help!
Matt
Looking at how the upper and lower ac control valves fit together, I don't see how there couldn't be a leak there. The pieces do not fit tightly together. There is a sizable gap between the three pieces (upper and lower valves, and the plastic disk with pivot arm on it that goes in the middle).
Wombvette mentioned replacing a plastic pivot rivet that generally breaks, causing a leak. I didn't appear to have any rivets that were broken, it just isn't a tight fit. Is it supposed to be a tight fit? Is the lack of a tight fit causing the leak, or is something else the cause? I guess that I don't quite understand how this valve works.
Also, my heater blower switch has problems. It doesn't change speeds as you change positions on the switch. It will go into high mode, but only if you push the switch all the way forward, then bring it back a half detent. Is this indicative of a faulty switch?
Thanks for any help!
Matt
02-29-2004, 12:12 PM
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Re: vacuum leak in heater/ac control (80Matt)
Your vacuum leak could be at where the vacuum hose comes through the firewall grommet. This is a common place where the hose get chafe.
If you only have high speed on the fan switch this could be a few things:
1. Bad fan switch
2. The blower motor relay on the firewall
3. The restat on top of the A/C box.
If you only have high speed on the fan switch this could be a few things:
1. Bad fan switch
2. The blower motor relay on the firewall
3. The restat on top of the A/C box.
02-29-2004, 02:36 PM
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Re: vacuum leak in heater/ac control (80Matt)
Yes, the 2 pieces need to be held tightly together by the rivet. Besides replacing, it is also possible to tighten this &/or lube w/ a thin layer of white lithium grease or vasoline to fix.
03-11-2004, 07:31 PM
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Re: vacuum leak in heater/ac control (Ganey)
Allright, I did a little more searching.
The leak is at the valve. I can hear the hissing with the engine running and the valves connected. With the valves disconnected and the engine running, I can hear the hissing coming from the A/C Control Switch-Vacuum Valve (This is the one that all the hoses plug into). When I tape over the holes at the opposite end of the A/C Control Switch, the hissing goes away. Therefore, I conclude that the leak is at the connection between the end of the A/C Control Switch with the little holes, and the white plastic pivot disk (not sure of the name) that attaches to this.
The white plastic disk spins in conjunction with the position selected by the Htr/AC control lever. It is attached to the lever at a pivot point, allowing it to spin with changes in positions of the lever. I'm not exactly sure how this works, but I'm guessing that it selects temps or heat/ac by covering and uncovering combinations of those little holes on the A/C Control Switch. I would think that a tight fit would be required between this white disk and the A/C Control Switch.
When I put the parts back together, I have nothing that forces the white disk to fit snuggly against the A/C Control Switch. Am I missing something? I believe that the lack of a tight fit here is what is causing this leak.
Any help is appreciated.
Thanks,
Matt
:skep: :skep: :confused:
The leak is at the valve. I can hear the hissing with the engine running and the valves connected. With the valves disconnected and the engine running, I can hear the hissing coming from the A/C Control Switch-Vacuum Valve (This is the one that all the hoses plug into). When I tape over the holes at the opposite end of the A/C Control Switch, the hissing goes away. Therefore, I conclude that the leak is at the connection between the end of the A/C Control Switch with the little holes, and the white plastic pivot disk (not sure of the name) that attaches to this.
The white plastic disk spins in conjunction with the position selected by the Htr/AC control lever. It is attached to the lever at a pivot point, allowing it to spin with changes in positions of the lever. I'm not exactly sure how this works, but I'm guessing that it selects temps or heat/ac by covering and uncovering combinations of those little holes on the A/C Control Switch. I would think that a tight fit would be required between this white disk and the A/C Control Switch.
When I put the parts back together, I have nothing that forces the white disk to fit snuggly against the A/C Control Switch. Am I missing something? I believe that the lack of a tight fit here is what is causing this leak.
Any help is appreciated.
Thanks,
Matt
:skep: :skep: :confused:
