The ac in my 1999 3500 will work for a few seconds then you hear a pop under the dash like a vent closing then its nothing but the heater blowing. I looked under the dash for comething broke or loose but dont see anything. Any sugestions?

 

Start it and turn the air on. Now crawl under the front and watch the compressor/clutch set-up. Is it slipping?
That is what mine did last summer. Clutch fixed it.

 

I will take a look at that in the light. Thanks.