Sometimes it works good other times it will blow out of defrost only. If I keep turn it off and on it will eventually work right again. Checked the vacuum lines and they seem fine. Is the check valve a universal thing or its it a dodge only part?

 

What year are we talking?

You can find a "universal" check valve. Make sure there are no leaks in the vacuum lines too, including the ones to the HVAC controller.

 

Its a 1999 Dakota 5.2L I took the bezel off and took the screws out of the climate control panel and looked at the I couldn't find a vacuum line going into it. Where does the vacuum line go to inside the truck?

 

It's a hard plastic line, not your typical soft rubber line that you'd see under the hood. It should pass through the firewall somewhere near the booster.

On the HVAC control there is a plug with 8 lines of various colors.

 

Ok so I took off the 2 check valves on by the brake booster and the other one that is down by the firewall that comes out to the hard line. I blew through them and checked to see if they was functioning properly and they seem to work fine. I put everything back together and now it seems to he working good. Could it have been something in the check valve keeping it from operating?

 

A bit of dirt or something could make the valve not work quite right, but, that should only be an issue under relatively heavy load.....

 

Not fixed. Doing the same thing again. It wont work if you try to turn it on while driving. It will only work if you are idiling and turn it off and on a bunch of times with the fan on the lowest setting.

 

Still have a vacuum leak somewhere.

 

If I do it must be inside the dash somewhere. I used almost a whole can of starting fluid and sprayed all the vacuum related stuff in the engine compartment and got nothing at all.

 

You also have a vacuum reservoir under the windshield cowl/vent it could be cracked or a leaky hose.