2000 Silverado. After work, went to start my truck, and battery was dead.
Had a friend jump start me, and when I attached the jumper cables, the heater motor started running.
Jump started the truck, and everything seemed normal, except I couldn't turn the heater fan off, or adjust speed.
When I got home, I shut the truck off, but the heater fan motor kept running.
Have decided it is 1 of 3 things...
Ignition switch went bad.
Heater switch shorted out
or
resistor in heater motor circuit shorted out.
Would like to fix it, and can, but don't want to buy all 3 pieces, and add until I eliminate the problem.
Anyone out there had the same problem, and what was it?

 

Welcome to the forum. Is the blower running at the highest speed? If so, the integrated relay in the blower motor resistor assembly is not switching out of that setting. Pull the FRT HVAC fuse from the underhood fuse block to cut the power to it for the time being. The blower motor resistor assembly is usually located near the blower motor behind the passenger side insulator panel under the dash.

 

That is exactly what had happened. The only thing I've never seen, is that the heater motor keeps running when the key is shut off. I've seen where there is only one fan speed, and knew it was the resistor. I had decided to replace the resistor/relay assembly as a first step, and it did the trick. It was a cheap $28.00 fix compared to $117.00 if it would have been the blower motor switch.
Thanks!

 

Glad to hear. Thanks for the update.