I was investigating why my 2000 GMC Sierra 3500 (old body style) truck wasn't getting very good air flow out of the vents and discovered some HACK has been in the air plenum where the heater core goes and cut it up to apparantly replace the core. Does anyone know where I can get a diagram of the inside of the plenum? The hack used a piece of metal ran into the box with a drywall screw to keep the core in place - friggin idiot! So now I need to know exactly what I need to get it repaired.

Also what is the best way to clean the evaporator with it still in the truck. I was thinking either some degreaser and compressed air or maybe an aerosol can of throttle body cleaner or maybe even brake cleaner. I thnk this is my air flow problem. Any thoughts? Thanks

 

I do believe the service manual has a diagram in it. I have gone to my local GM dealer several times to get copies of pages of the service manual, sometimes the parts dept can print it out of the computer.

 

I got one today from the dealer. It isn't the best, but gives me an idea of what I am looking at. Thanks for the response!