Chevy & GMC Vans

Am I correct in my thinking that the rear heater control valve is vacuum controlled? That a vacuum leak will result in NO rear heat?

you are correct..

That's what I thought. Turns out that when the alternator was swapped out, a vacuum hose came discombobulated.

Where can I find this valve that controls the rear heat.
I have a 2000 that I just bought, rear heat only blows cold. I was told to check this valve but dont know where it is, or even how to check it
Thanks

I may be wrong, so PLEASE don't quote me.

I think they're all under the frame somewhere on the right side behind the doghouse opening. Usually, the valve doesn't go flooey; it's the vacuum line itself. If the vacuum line is flooey, you'd notice it because you won't have air going anywhere except the defroster.

The rest of my heating system is working fine, dash vents, def and floor modes all work. So I will check for this valve.
Is there a way to check the valve before replaceing it? Can I apply vacume to it with a vacume pump?

Under the hood next to the heater box you will see the valve. It is electrically controlled with a solenoid which allows vacuum through to open the valve. Chances are your solenoid is bad, you can confirm with a handheld vacuum pump. Pump it down and see if it lets the water through.

Scott

Here's a link to a photos of that solenoid from my 2001 - might help with the locate - I just disconnected and bypassed it and water always flows now - including in the summer - hasn't cause any issues for me

http://www.flickr.com/photos/7474654@N04/1471062090/
http://www.flickr.com/photos/7474654@N04/1470200567/

So there is a vacume operated solinoid down below the ac drier, where is the valve that was also mentioned, or is the valve and solinoid one in the same?

If I apply vacume to this solinoid, and the solinoid is bad, it wont hold vacume and send water to the rear, is this correct?

Thanks for the pics, it helped a lot.

I just went out and looked at mine, its all connected and looks like it is all one unit, solinoid and valve. Correct? Can one part be replaced with out the other?

They are sold together.. But it is a solenoid, and a vacuum diaphgram. You can apply vacuum directly to the diaphram directly for testing. Or, leave vacuum on it all winter long. I think it cost about $60 canadian from the dealer last summer for the part.

You can change just the solenoid though, but you have to buy it all. It unclips, so at least you dont have to pull apart the hoses.

Scott

OK, I had vac going to the solinoid (the top piece) but no vac coming out of it and going to the valve down below.

So I just ran the vac line directly to the valve for now, so the kids will have heat in the rear for the winter, I can just un-hook it come spring.

Thanks for the help.

U guys and this site have been very helpfull.

Thanks
Dan

My solenoid went bad too so I just hooked the vacuum up directly to the water shutoff valve. At least I get heat in the back now, but it takes the system longer to heat up if I just want it in the front.

Anyways, where did you see the solenoid sfeaver? When I went to the dealer, they didn't sell the solenoid separately, only as part of the whole water shutoff valve assembly for $200!

The thing I bought had the solenoid and one valve on it I believe.. It was part number 15070012, retail was 118.50, i paid 70.39 for it. It is seperate from that 6-way valve thing though from what I remember. That was May 28, 2007.

If they have raised the price on that solenoid/valve that much in a year, they can stick it.. No wonder there going out of business!! After paying $300 at a discount for those two pieces of tin that hold the side cladding on, I'm done buying GM parts. I find you can buy the same part made by the same people for a lot less from a parts store. Gm doesnt make much of there own stuff anymore.

Scott

Thanks to The Valley Boy and the rest of you...I finally found this thread after 2 months searching on the net......trieds flushing the rear core as someone else suggested..still no heat...and today I bought a foot of 5\32 vacuum and as a back-up a 90 degree connector.
Good thing I did, because I would have had a hard time getting the existing hose off the valve underneath at -12C and the sun going down quickly!...lol
Just disconnected both hoses off the solenoid and coupled them with the 90...instant heat in the back!!

Thanks so much

Glad we could help. By the way, I grabbed another solenoid at the junkyard and it works perfectly now.