you have a fuse out...
2001 dodge ram 1500 ac and heater flow regulator switch does not work. works only on defrost. How to fix?
Heater core is leaking
Common heater damper door indexing problem. Our 2000 back up shop truck hot is cold and cold is hot on the controls. Expensive to fix and usually requires a trip to the dealer
Maybe a bad heater core
A leaky heater core can do that. Also if the AC is not operative, the defrost mode can't dry the cabin air.
Was it coolant? Possibly a leaking heater core.
If the heater core is ok, check to insure your ac unit is working. The ac works in conjunction with the heat when running defrost, and without the ac air windows will fog up .
You have to take the trunk floor out and the battery will be on the right.
You should probably bring it to a mechanic because it is very difficult to replace the heater core on GMC pickups.
unfortunatly m8 u have to take the dash board out to get at it
mercury villager heater core 2001
Check for a vacuum leak either under dash or under the hood Check the operation of the vacuum actuated motors under dash Check the selector switch