Teal95Jimmy

I have the manually controlled knob for my hvac. The selector has started leaking the vacuum it recieves and will not change the vent setting, which means its time to replace it. I was on the advance website, what is it called?

Teal95Jimmy

anybody

Rick Norwood

How do you know the control is leaking? Please describe more of your symptoms. Are you getting all of the air blowing out of the defroster vents regardless of the setting on the control? What works and what doesn't work?

I also assume that this is on a 95 Jimmy, Please give us make, model, year engine size etc. and be as specific as you can with your problem statement.

Teal95Jimmy

I have a 95 Jimmy 4x4 2 door vortec v6 (w)

In any position it stays in the defrost vent mode, the vacuum lines on the back of the unit are all tight and are not leaking. but the air conditioning compressor will kick on in the ac and defrost modes. i do not have a problem with contolling the blower speed or temperature, just the vents it will come out of.

As i said earlier i can hear the hiss of air non stop coming from the switch in every position

twillers

Teal95Jimmy,

If in fact it is the heater control valve, consider yourself lucky. I have a 99 S10, with a bad control valve. To fix mine you need to replace the whole switch assembly, which includes the temp, fan, and mode select assemblies. The vaccum switch alone is not replaceable. In your case it is. If you go to Delco's website, (http://www.acdelco.com/html/catalog/index_auto.htm), and enter your vehicle info, you'll find the part # (15-72151 HVAC / HEATER CONTROL VALVE ) listed under HVAC. This link will show you a picture of the item.
http://198.208.187.182/internet/Part...rtnbr=15-72151
Rockauto.com has it, $17.97. Here's the link, http://www.rockauto.com/catalog/cata...&parttype=6860.
gmpartsdirect.com has it for $15.18 GM part #16198927
Being it's a Delco item, you should be able to get it from any auto parts store that handles Delco. The only reason I know all this stuff, is because I was looking for a replacement on my 1999 truck. Hope this helps.

twillers

Rick Norwood

Check to make sure the vacuum lines attached to the Black Vacuum ball under the hood are attached and are not leaking. If the air is blowing out of the defroster vents only, there is a good chance that you have a vacuum leak at the ball or one of the connections coming from the manifold that connects to the ball. Trace the vacuum lines from the ball all the way to the manifold. If you find any leaks or disconnected vacuum lines, replace them.

On my 93, there is a short length of vacuum line that attaches to the rear of the Plenum that is only about 1 inch long, that connects to a "Y" fitting that has two other lines attached to it. Since the heat is pretty high behind the plenum, I am constantly replacing this short piece of line. It is also real easy to knock loose when working on the rear of the engine.

Teal95Jimmy

All the vacuum lines are tight and only about a month old, the only place i found vacuum to be leaking is at the heater control unit

Cailen

Think I remember reading somewhere that this was because of some grease that wasn't applied properly on these switches at the factory causing them to leak down the road. If you can't find a new switch you might try regreasing the fitting on the back.

Good luck.

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tmjohnson

I am also having the problem of air only coming our the defrost, but I also have no heat. If it is a vaccum problem, would this affect the temperature as well?

rlith

It may not be the HVAC control itself that's actually leaking, it may be the main control diaphram under the dash (just left of center). These are known to go bad... The noise from the bad diaphram/actuator may be traveling is all.

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