how can i test my HVAC switches?

**kawasaki_kid** · 06-08-2009, 07:08 PM

Recently i have been having issues with my HVAC controls. the switch that controls where the air blows(def, floor, vent...) isnt working. my a/c switch only lights up when the fan is off, and if i turn my fan to high to hard, it just shuts off. my question is how can i test to make sure its the switches that are the problem, before i replace them? i would hate to throw $225+ at the switches and have it not work. thanks guys.

**daddytech** · 06-09-2009, 12:12 PM

no you are on the right track with the switches. my wife's 98 suburban was the same way, hers the fan motor went out first. then when i replaced that the fan the only level it would work on was high. her switches were bad but she is the kind that if it's on it has to be on high any way so i never bothered changing the switches out on hers but i did check all the fuses and checked the level controls for DEF , Floor, Vent and high/low and all of those work on hers it's just that the fan didin't work on anything but low and high ( might actually have been the wrong fan on hers honestly but it works and she's happy so my job is done here) lol

**missingremote** · 07-03-2009, 04:45 PM

daddytech, How easy is it to access or remove the switch or switch pannel? I want to inspect mine because I have the same problem. Fan speeed and/or vent selector Switch inoperative.
1995 suburban

**chevylurker** · 07-03-2009, 06:36 PM

I'm working on a similar issue and have found some help inthe electrical forum. I have replaced the relay and the dash switches to no effect. There are some "re-setting" tips suggested, and "code scanning" but I haven't found the solution yet; other than not spending $225 for something that won't make a difference.

p.s. Parts Planet and other recycling places can give you the smae items for less than half.

**daddytech** · 07-06-2009, 10:53 AM

my wife's, snap in with clips on her dash and it has 5 or 6 plugs on the back, if yours ar ethe same shouldn't be hard at all to change out, the hard part is the money they cost for the right one, they aren't cheap at all , I reccommend a pull it yourself site if you can find one that has the controls in it still.

**daddytech** · 07-06-2009, 10:56 AM

Originally Posted by chevylurker

I'm working on a similar issue and have found some help inthe electrical forum. I have replaced the relay and the dash switches to no effect. There are some "re-setting" tips suggested, and "code scanning" but I haven't found the solution yet; other than not spending $225 for something that won't make a difference.

p.s. Parts Planet and other recycling places can give you the smae items for less than half.

part of the heat and AC controls is still vacuum controlled too, it's not all electronic. might check the vacuum lines going to yout ac components if not it may very well still be a relay that's only intermittently not wortking

intermittent problems are the worst.

**chevylurker** · 07-18-2009, 02:59 PM

Thanks daddytech, but I know mine has to have something to do with a relay switch or module because, depending on my start up method, hot and/or cold air will blow from all the various places it should, but it always settles on coming through the defrost vents.
kawasaki_kid, did you ever find a solution/answer to your question?

**bill190** · 07-19-2009, 12:40 AM

These things can be quite complex electrically, so it is best to have a factory wiring diagram and a multimeter for testing. The complete wiring diagram would be in a GM factory service manual set.

The reason you need a "complete" wiring diagram is because the wires in a vehicle are all wrapped up in bundles, concealed, and hard to get to. So you can't exactly go tracing wires to see where they go!

Also the wires go to "black boxes" with just part numbers on them. What is that box for? What does it do?

This is all explained in the factory service manual set along with detailed troubleshooting instructions, locations in the vehicle of various parts, connectors, etc. Wire colors in the circuit, pin outs of the connectors, etc.

Anyway get the right tools for the job. BIG help!

Then as to if you can take apart a control panel to test the switches or clean the switches. Some of these are easy to take apart. Others impossible. Many times these switches need cleaning. (IF you can take it apart to clean them!)

So what you can do is pull the panel from a vehicle in a wrecking yard. Then see if you can take that one apart. If you wreck it, then no big deal. But if you can take it apart and clean the switches, then use that in your vehicle or also clean the switches in your vehicle and have a spare.

Best to put a dab of "dielectric grease" on electric switch contacts. You can get this at auto parts stores.

**kawasaki_kid** · 07-19-2009, 11:16 PM

Originally Posted by chevylurker

Thanks daddytech, but I know mine has to have something to do with a relay switch or module because, depending on my start up method, hot and/or cold air will blow from all the various places it should, but it always settles on coming through the defrost vents.
kawasaki_kid, did you ever find a solution/answer to your question?

well i replaced the control board, didn't solve all my problems. still cant get max fan to work, all the ac switches seem to work now, i can hear stuff changing when i hit the switches, its just not cold. The switch controlling where the air blows was all but fixed, except i couldn't get it to full dash, played with the actuator, lubed it, and now its good.

i guess i need to probably get a recharge, and change the resistors in the fan itself, another $50.

**bill190** · 07-20-2009, 12:41 AM

Good job! Sometimes there is more than one problem.

Also there are pressure switches in the A/C lines. If too little refrigerant or too much, the compressor will not turn on.

And the blower resistor and *connector* and the wires to the connector is a common problem with not all fan speeds working.