Rear A/C makes a thumping/clicking sound

[BigMic]

I'm new here, not technically proficient with cars, and I tried to search my problems in other threads so go easy on me....

My wife's '02 Mountaineer has a clicking/thumping sound coming from the rear A/C. The air works fine, blows hard and cold, but when you turn on the rear A/C it starts...thump...thump...thump. If you turn it back off it turns into a click, kinda like the sound of a turn signal. I took off the rear panels covering the A/C to try and locate the problem but I don't want to disassemble the "core housing", if that's the appropriate name for it. Has anyone ever encountered this problem or have any ideas?

One other thing, I never noticed this until I removed the panels covering the rear A/C but when I accelerate on the gas there is a hissing sound coming from back there. When I let back off it stops, press and hisses some more.

Any help would be great, wife is giving me **** on a daily basis by now.
Thanks,
Mic

 

[ntdawg13]

My Mountaineer has the same problem. I looked at a chilton's manual and I saw that there is a temperature blend door actuator and an air distribution blend door actuator on the back of the core assembly. When I move the temperature control it stops the thumping so I think I need a new temperature blend door actuator. Maybe that is what you need also.

Does the air distribution blend door actuator move the air from the overhead vents to the lower vents?