1996 GMC Sierra Heat Defroster Controls Not Working

This controls the temperature of air coming out of the vents. When they go bad, the air stays cold or hot and you cannot adjust it.

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I have a 1996 GMC 3500 Sierra 7.4 Litre. Battery cable came loose, arced and blew fuses. Replaced fuses and all was well. later, when I tried to turn on defrosters- I have absolutely no controls working at all (Heat/Defrost). Blower is running on high, but are cold. I have 2 buttons (AC and Recirculation)(Ext. Cab) and the lights in those do not come on at all when pressed to “on” position. Is this the Heater Controls that have went out?This controls the temperature of air coming out of the vents. When they go bad, the air stays cold or hot and you cannot adjust it.

Yes, it sounds as if you may have smoked the control head or mode door actuator motor as well when the battery cable arced. You may also want to check for any burned or melted wiring that may accompany events like that.

I have been all under the dash, but all wires seem okay. But you do bring about another question: My cigarette light continues to blow a fuse. I switched the sockets, but same thing. WHY?

Are you actually using the lighter element, or using the outlet for a charger/adapter for a phone,etc?

I switched using the power outlets.

I understand that, but what I’m asking is…does the actual lighter itself blow the fuse, or does it blow when you put in something else into the socket?

Blows when I push the lighter in. Cigarette lighter gets red, but now have to replace fuse again. Three times in succession.

You have a bad element, probably partially touching internally and popping the fuse. Try another lighter element and you should be fine.

Did that with brand new one- same results.

Brand new GM one, or aftermarket one?

Aftermarket. But on this same question. The other day I plugged a power inverter into the “Power socket” and the red light pulsed and would not power the vac. Sorry so many questions, but I fear that all are related.

First, I’d recommend trying a lighter element that is actually made for you vehicle from GM. A generic one bought at any other store is not made for your particular vehicle. All lighters are not the same. As for the power inverter, can’t help you there, it could be a bad part, or not getting enough voltage to power a device. If you continue to blow fuses, I would suggest installing a GM socket and element assembly and go from there. If you still pop fuses, there has to be a wiring issue somewhere.

Thank you! Guess I gotta spend that 100 bucks on new Heater Control, and i’ll get that lighter element from GM. Guesstimate for me what it might cost just to have the wiring checked (not fixed, just diagnosed?

You’re welcome. To diagnose wiring problems get more involved than pretty much any other problem on a vehicle. You will most likely pay ‘straight time’ for the tech to diagnose the problem. That means, for as long as it takes to find a problem, you’re paying by the hour at whatever that shops labor rate is.

I’m a mechanic- but no good with wiring at all. Life! Thank u again.

Sure thing, have a good night.

Does a 2007 GMC Sierra have a cabin filter?

ProTech: Do you have a Denali Sierra, or just the regular Sierra pickup?

Just regular pick up SLT.

There is no cabin air filter on your truck.

Great, thanks.

GMC Dual Batteries

Can the two positive cables on a 96 sierra be broken up with a dual post battery, or do they have to remain together?

Answer: The cables must stay together. In order to make the truck a dual battery system requires a little more than just adding a battery.