I just bought an old truck. Oh, 6 GMC Sierra with a wonderful wonderful heater, and the next day the fan went out. What should I check first?

Could it possibly be a fuse?

Thank you in advance

I would start at the owners manual. See where the fuse/relay is.. See if the plug has juice at the motor. If it does replace the fan. If it does not check the relay in the fuse box. If it is working but no juice going in check the switch.

Thanks Danny

Fan not work at all or will it run on the highest speed only?

Usually they growl and make noise when they start to go bad. If it didn't make any noise and just quit all together I would suspect electrical, likely a fuse. I would start there like Danny suggested.

If its all speeds, likely the motor. If hi speed still works likely the resistor board.

I have a 05 Chevy Silverado 1500, I have had to replace the relay for the heater fan blower several times already since I have owned it. Sometimes your blend fan will go out also I have found on mine also.

Can't help but sounds like great advise. It is always something!!!!

Resistor box in behind the glove box.

It's up underneath the passenger door well area, you may have to remove a trim panel to actually access it. Smack it with a hammer while you have it switched on high speed, you'll likely find that it'll start blowing again. The hammer jiggles it just a little bit so the motor isn't sitting in a dead spot. If that's the case you need a new fan. It'll probably even keep working until you can get a new blower motor, but keep the hammer handy. I've done tons of them.

What if it only works on high speed?

Resistor??

I need to fix mine

It is most likely the resister panel. Just changed mine on a Ford 150. It was behind the glove box, two bolts and a plug. Make sure to clean the contacts where the board goes into the fan compartment. It took about 15 minutes to change.

Nice!

Thanks

You should be able to unplug the fan and run direct power to the fan plug to see if the fan works. If it does you have an issue between the switch and wiring running to the fan.

Fuse first just replace it with a known good one, resistor next then the fan might be the issue. like said run a hot wire to the fan to test that before you rip into it.

My 06 was the speed selector wiring harness, they now have redone the new harness with heavier wire.