Problems with 1999 Chevy Silverado 1500 (5.3 Litre V8) Heater Switch?

[MommaM]

No output when switched to setting 4 or 5. Lower settings work just fine. I have replaced the resister switch and tried a new control switch. Still does not work. I also replaced the cab air filters. Any suggestions ??

 

[LSx Racer]

There is a plug on the passenger side under the dash, about where your feet set. Turn your key to the on position. Turn on your a/c to 4 or 5 one of the settings that don't work. Now get on the passenger side and wiggle that plug if your a/c starts to come on and off then the is your problem. It is common on the newer GM trucks.