1997 dodge ram 1500 , how does the vents work for floor, defrost etc. I know it works by valcume but is there a pump somewhere. Can not get it to change it is stuck on defrost ( window ) it has some suction but not a lot. How much should it have. Nothing is broke on the controls.

The vacuum for the vents comes from the engine. There should be a check valve and reservoir in the system. The check valve is probably mounted near the power brake booster. It's a one way valve and it can fail. Be care of which way it is mounted.

If you've located the connector at the heater controls, on a Dodge the black line is usually from the vacuum reservoir (source). It should have a pretty good suction on it when the engine is running at idle. If not, check the check valve and the lines for leaks.

Where would be the vacuum reservior and check valve located?

The check valve should be near the brake booster, usually where the large diameter vacuum hose comes from the manifold. They would be a small tap off the line with a smaller diameter vacuum line coming off it.

The reservoir can be mounted under the hood or may be mounted under the cowl.

It turned out to be a bad vacume hose at the engine.