heater control valve
Thread Starter
Instructor
Joined: Oct 2006
Posts: 223
Likes: 5
heater control valve
The heater control valve was leaking on my 85. Part has been discontinued by GM, not available through the usual places. ( CC, Ecklers, etc. ) The guy at Car Quest found one that looked simular, so I hacked the old lines and put the new one in. Now when I hook up the vacuum line, all I can get is cold air. If I unplug the vacuum line, everything works fine. Any ideas?
Pro
Joined: Oct 2004
Posts: 504
Likes: 82
From: Melbourne Victoria
When you move the temp slider over to hot is the vacumm shut off to the heater valve ?
ie when on cold setting vacumm is present and the valve is closed and coolant bypasses the heater core.
when on hot setting vacumm is not present and the valve opens and allows coolant to flow through the heater core.
This is how it works on my 87 with manual AC, not sure if 85's are the same.
ie when on cold setting vacumm is present and the valve is closed and coolant bypasses the heater core.
when on hot setting vacumm is not present and the valve opens and allows coolant to flow through the heater core.
This is how it works on my 87 with manual AC, not sure if 85's are the same.
Burning Brakes
Joined: Apr 2004
Posts: 762
Likes: 2
From: Huntington ma
The '84-'85 (manual only) control unit is the same as all other year's with the manual option.
The temp control slider not only moves a manual cable that controls the temp mixing door, it also makes a vacuum switch (when all the way to Cold) that "sends" vacuum to the shutoff valve causing that valve to close and not allow coolant to pass through the heater core.
Assuming you have vacuum at the dash control unit (if all of the function doors work - vent, A/C, heat etc.) then check the vacuum line at the control valve - there should NOT be vacuum there with the temp control slider moved away from the full Cold setting (car running, of course). If there is, then the control unit needs to come out of the dash for a closer look.
There should also Be vacuum at the control valve with the temp control slider moved all the way to Cold...
BTW - I got a new valve assembly for my '85 from Ecklers just a couple of years ago - is it now unavailable?
The temp control slider not only moves a manual cable that controls the temp mixing door, it also makes a vacuum switch (when all the way to Cold) that "sends" vacuum to the shutoff valve causing that valve to close and not allow coolant to pass through the heater core.
Assuming you have vacuum at the dash control unit (if all of the function doors work - vent, A/C, heat etc.) then check the vacuum line at the control valve - there should NOT be vacuum there with the temp control slider moved away from the full Cold setting (car running, of course). If there is, then the control unit needs to come out of the dash for a closer look.
There should also Be vacuum at the control valve with the temp control slider moved all the way to Cold...
BTW - I got a new valve assembly for my '85 from Ecklers just a couple of years ago - is it now unavailable?
Racer
Joined: Aug 2007
Posts: 260
Likes: 2
From: Pensacola Florida
So are you saying that your heat and a/c work normally without the heater control valve in place? I am looking for one myself cause it looked to me like the previous owner disconected mine because it rusted apart...still laying in pieces just below where it normally would go. I imagine everything would work alright as long as the blend door was doing it's job. I cant even find a picture of it or the heater hose routing in my GM service manual or my chilton for that matter....
Instructor
Joined: Jul 2007
Posts: 229
Likes: 0
From: FT Lauterdale Florida
when mine took a dump, or a pee! hahaa, I ran some heater tube and by passed the heater core all together. my ac works great.
the heater on the other hand will only blow cold air at me, since its not hooked up.
works good in south FL.
the heater on the other hand will only blow cold air at me, since its not hooked up.
works good in south FL.
Racer
Joined: Aug 2007
Posts: 260
Likes: 2
From: Pensacola Florida
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Team Owner
Joined: Jan 2003
Posts: 20,316
Likes: 246
From: Summerland B.C. Canada
So are you saying that your heat and a/c work normally without the heater control valve in place? I am looking for one myself cause it looked to me like the previous owner disconected mine because it rusted apart...still laying in pieces just below where it normally would go. I imagine everything would work alright as long as the blend door was doing it's job. I cant even find a picture of it or the heater hose routing in my GM service manual or my chilton for that matter....
I believe GM eliminated the valve in 88, 19 years before me.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
The water shut off valve for the heater was only used in the 1984 -1987 cars. When I bought my car at 3 years old, the water valve had already been eliminated. Both the heat and the A/C work perfectly fine without it. I didn't even know there had been one, until I stumbled across it in my parts book, one day.
My FSM shows it in two different illustrations. One of the vacuum water valve and the other showing the heater hose routing.
RACE ON!!!
Originally Posted by 1irishprince
I cant even find a picture of it or the heater hose routing in my GM service manual or my chilton for that matter....
RACE ON!!!
Racer
Joined: Aug 2007
Posts: 260
Likes: 2
From: Pensacola Florida
The water shut off valve for the heater was only used in the 1984 -1987 cars. When I bought my car at 3 years old, the water valve had already been eliminated. Both the heat and the A/C work perfectly fine without it. I didn't even know there had been one, until I stumbled across it in my parts book, one day.
My FSM shows it in two different illustrations. One of the vacuum water valve and the other showing the heater hose routing.
RACE ON!!!
My FSM shows it in two different illustrations. One of the vacuum water valve and the other showing the heater hose routing.
RACE ON!!!
That's why I was asking...There was a shut off valve...sorta like a petcock valve, but I thought that someone just added that since I couldn't find an illustration. You must be talking about the red shop manual, I have the blue GM Factory Service Information manual...and in the index under heating and ventilation it states "Not Used"..but the tab is still there...just no pages. Guess I'll have to break down and get the red one!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
My manual is (was) light grey. I think some years use different color covers. The water valve is vacuum actuated (or deactivated) not operated like a petcock. It sounds like you have a manual valve subbed in for seasonal operation. Either way, you don't need it.
RACE ON!!!
RACE ON!!!
Racer
Joined: Aug 2007
Posts: 260
Likes: 2
From: Pensacola Florida
My manual is (was) light grey. I think some years use different color covers. The water valve is vacuum actuated (or deactivated) not operated like a petcock. It sounds like you have a manual valve subbed in for seasonal operation. Either way, you don't need it.
RACE ON!!!
RACE ON!!!
