Heat only works after I hit a bump with fan speed set to max

[JustinLM]

I have a 2002 quad cab 4.7. My Ac works fine but my heat will only work if it is on max, and after I hit a bump or make a sharp turn sometimes, it makes a clunk sound then the heat works. The fan blows fine all the time, I’ve flushed the heater core aswell. Everything else works fine, my recirculation door is gone, but I don’t believe that’s the problem considering the heat will work fine once I hear the clunk, it continues to work until you turn the fan speed to the lowest then you hear a light clunk, like something falling then it blows normal air. Please someone help me.

 

[jws123]

yeaa.. It sounds like you have blend door issues on older rams the plastic cracks and doors fail time to tear the dash out. It is honestly not that bad of a job can be done in 1 day if your mechanically inclined tons of vids on youtube on how to do this they sell replacement doors I would also do the heater core and evap while your there.

 

[JustinLM]

gosh that sounds like a lot of work, I’ve seen videos about it hoping it wouldn’t come to this, I just wonder what causes that clunk and then the heat works.