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93 GMC Sierrra - heat stuck on after being jumped

Hey all,

So I had to get a jump the other day after leaving my lights on. Since then, the electronic controls for the heat/ac is completely off (black screen) and the heat is stuck on. I checked the fuse and it’s fine. Someone suggested a relay, but from what I could find, there is only one 3 pronged and one 5 pronged relay, so I wasn’t able to swap them out to see if that was the problem. Figured I’d ask you guys if that sounds like a possibility? I am admittedly terrible with cars, so who knows if I was even looking at the relays. Found the box under the fuse box in the cab.

Thanks for any help.

These screens routinely go blank. The HVAC head is part of the radio (odd)You are going to have to get a new head (you most likely will have to get the reciever part the head plugs into also,as they are a part number match).

Thanks. Would that also explain it being stuck on heat? What kind of price am I looking at with that? Thanks again.

I would have to agree with oldschool. This head unit is going to have to be replaced. I would recoment a junkyard. Getting a brand new one from a dealer or even aftermarket could be impossible. A junkyard one would be just as good.

I was installing refurbished units (we called these 3 piece units as they had the head,the reciever and the cassette seperate)as late as 1999,time really flys.I think there even was a cassete with a EQ offered.

I have no idea why the heat is on (unless it is part of the failure) it was always blank or semi blank displays that made me replace these.

The problem might be with the control modules for these circuits. On some GM vehicles, if the battery is disconnected or if it goes dead, the modules can go to sleep and never wake back up. When that happens, the modules require replacing.