10A HVAC fuses keep blowing

Red_Sierra · February 14, 2025

Hey y'all, I gotta 2011 GMC Sierra 1500 SLE 4Dr 4.8L V8 with dual zone climate controls. For whatever reason I can't figure out yet, fuse 39 or 55, the two that control HVAC, keep blowing on me. If it's not one, it's the other, they'll work when I replace them for a little bit, then they'll blow on me again. Anyone got any clue what could be going on?

davester · February 15, 2025

what have you done to actually try to figure what is causing the fusse to blow?

Red_Sierra · February 15, 2025

I've checked over the wiring for damage or corrosion, didn't find any, checked the blower motor resistor to see if it was blown, it wasn't, blower motor doesn't have any abnormal sounds coming from it during operation.

The only other thing I can think of is that the blend doors may be due for replacement and it's blowing the fuses but I don't know if that would cause it.

The main reason I know a fuse has blown is the air switches from any vent I want to only floor and defrost vents.

It seems #55 likes to blow completely, but #39 the prongs get burnt.

davester · February 16, 2025

Well, I would suggest a subscription to alldatadiy.com for your truck, so you can see what the wiring diagrams for the truck look like for those circuits.

The blow motor and resistor pack connectors, and mates on the wiring harness, also commonly get burnt and cause problems.

And if the fuse is getting burnt, then the contacts in the fuse box are also probably messed up, and that will perpetuate the problem.