I have a 94 1500 4x4 5.2L. When the A/C is on and you put the engine under a load(ie) going up hill the A/C goes from coming out of the vents to coming out of the defrost. When the load diminishes you can hear a clank inside the dash and then the A/C comes out of the vents again. Any ideas?

 

Maybe a vacuum leak? I know my heat did this and it was because I had a vacuum leak. I'm not sure if it does it with A/C too but my guess would be that it does since these are the exact same symptoms I had only with A/C instead of heat.

 

Thats what I had suspected. Any ideas where to look for it at or where to start looking?

Thanks

 

common problem. check the vacuum lines for breaks, incuding cruise line. if they're ok, replace the quarter size check valves in the vac lines.
https://dodgeforum.com/forum/2nd-gen-ram-tech/170881-is-this-it.html

 

Check the 2 check valves in the accessory tree that comes off the intake manifold. one is right where it connects to the intake. The 2nd is father up the line, in the tee near the firewall.

Both check valves are the round thick part of the connection and have rubber boots on both sides. They simply pull apart.

There is also a vac line that runs under the battery tray that occasionally splits due to corrosive fumes from the battery

 

dang, vaughan beat me.

 

Thanks you all I will check and replace them all when I change the engine. She started white smoking from the right tail pipe on the drive home. Only has 205009 original miles on the motor. I guess the Japs arent the only ones who can build an engine. LOL

 

Before you do a rebuild there is a couple of things you can do. First do a compression check to see if you have one or more cylinders and or valves that are bad. I have a feeling that you may have a bad head gasket since you said white smoke and not blue smoke which would indicate bad rings as oil is bypassing them. I realize that at 205009 miles your engine is getting tired but if it still has good power then maybe if it is a head gasket then it is a cheaper fix and can be done with the engine in the truck And if you do replace a head gasket then you will have the intake manifold off and that would be a good time to replace any vaccum line issues you may be having.