heater not working right??

[Mudracer80]

My heater quit working good, It will still blow kind of warm going down the road but not near as warm as it should be. When I'm stoped it blows even cooler. I'm thinking its some kind of vacume leak but dont know were to start. Any Ideas???

[npccpartsman]

If it's blowing out the vents correctly it may be that the heater valve isn't letting coolant through to the heater core. There is a vacuum line that operates the heater valve, but usually if you have a significant vacuum leak from the vacuum pump other things don't operate correctly. That little line is very easy to knock off and will make your vacuum pump run all the time. You can hear it with the key turned on and nothing else running. Normally it will run for just a bit then stop. If it keeps running you have a leak.

[Mudracer80]

See thats what is confusing me, usally if its a vacume leak the air will blow through the defrost, but everything is working normal it just dosent blow very warm at all and it blows cold while I'm stoped.

Could it be the vacume lines at my hubs causing this? I know that my 4x4 vacume line for the hubs are leaking because when I put it in 4 wheel the air blow through the defrost. However the heater has worked good before even with the hubs leaking.

[Pthompson]

Could be your cool/hot air door under the dash. The axle that it rotates on usually breaks not allowing a full shut off of cool air. Read up on this website. Might help you at least troubleshoot a bit, HeaterTreater.net

[05f250powerstroke]

Is your coolant low?

[Keith T]

I have to agree with 05f250 Powerstroke. Check your coolant. Could be your head gaskets need to be replaced.

[gary2070]

Tie that heater valve under the hood in the open position and see if it solves your problem.