Any auto mechanics-heating question

[thebayratt]

Originally Posted by GolfNut

Also, not sure about that van, but some rigs have a vacuum actuated heater valve that when triggered diverts the flow to the heater core.

My Dodge Ram does that at odd times. Its a vacuum valve thats screwy....
I can go down the road with just the "vent" on and all the sudden, it goes to the defrost air flow. I let off the gas or take off the cruise control (also vacuum actuated) and it goes back to "vent".

That or the thermostat is sticking... Get a "failsafe" thermostat. If the fail, they fail in the open position; so not to overheat your engine.


Look and see if your water pump is dripping any water out of the bottom of it. When they go bad there is a "weap" hole that water comes out. I had to change mine last summer bc of this.