ok guys ... need some help ... recently replaced radiator and water pump ... doesn't appear to be any air trapped in the system ... even followed the suggestion in the the thread with the other guy that has a heater problem as well (park on incline run with rad cap off until system warms up and opens) ... one thing i did notice while waiting on the system to open up was that the condenser fan was running while the heater was on ... not sure if that's correct or not since i have used the heater since i replaced the condenser fan in early summer this year ...

the air inside the cab is ice cold ... feels like the ac is on ... i turned everything off and let the engine run while at normal operating temp ... when i turned the heater back on i got nice hot air until the condenser fan kicked on ... this is what leads me to believe that it's the fan that's the culprit ...

any thoughts or ideas that point me in the right direction would be greatly appreciated ...

 

If you had the heater in defrost mode then that's why the a/c compressorand condensor fan was on. If not then there might be a problem with the HVAC control unit. Either way the air shouldn't get colder if you have the temp control to heat even with the a/c on...unless you have a problem with the HVAC mixer vent door. I'm still learning aboutthe ramsbut i'm sure it's vacuum operated...i'd check for leaks and look at any kind of actuator valves.

 

well all the vent doors seem to be moving properly and directing the air in the proper direction ...

 

anyone else have some insight?

 

Plugged heater core maybe? When it feels like the air is so cold the a/c is on, is the a/c compresser actually going when it shouldn't be (make sure you're not on defrost)?

 

the air is cold regardless of the setting ... whether it's defrost ... the face vents or the floor vents ...

i'm thinking that the problem is not the heater core since i do get nice hot air when i first turn on the air system (after the truck is at normal operating temp) but then i notice that the condenser fan kicks on and then i get freezing cold air

 

Check to see if the 2 heaters hoses going to the heater core are hot, make sure that the defrost is off, make sure that the snowflake is off. The compressor comes on when the defrost is on and this makes the condensor fan come on even if you have hot selected. let me know.....

 

both hoses hot ... one going to the resevoir tank is not as hot as the other if i had to guess i'd say approx. 20% cooler

turned vent selection to floor vents ... temp selection to hot ... fan speed to full snowflake off

results: air warmer but no warmer than ambient temps and condenser fan no longer spins (guess you were right about the defrost selection haha)

 

blend door seems to be functioning correctly i can feel and hear the change in the routing of the air

 

Doubt it's the heater core....notice any dampness on the passenger side floor or smell antifreeze? EDIT:What year is your truck and have you ever flushed the system?

I still think it's the mixer door...i'd look into it more if I were you. You usually won't hear the mixer when changing the temp....the routing doors you will though.