I need A/C / Heat help

[meyek91974]

'99 Exp EddieB V6

The rear A/C / Heat works fine, but when I push any button other than Vent for the front there's a repetative "clump, clunk, clump" sound at the right side of the dash. The sound continues if I push the Off button until it randomly stops or I turn the truck off and back on. Also, No air is blown from the dash. - at all, ever. (unless it's the trickle in air if I push Vent. I checked the fuse panels on the left dash and under hood and al seemed to work fine. I've never had to work on ac or heat, so... do you have any ideas?

 

[bobflood]

As I understand it, the flaps that control which set of vents the air comes out are controlled by vacuum motors, not electrical ones. If you pull out the HVAC control unit, you will see several different colored vacuum lines attached to the back via a vacuum manifold. Sounds like one or more of the lines, or the manifold itself, might be bad. You said air never comes out the dash - where does it come out? The "default" result if vacuum fails is the defrost vents. Good luck.

 

[my98nnj]

And to further the above post, if no air is coming out the defroster, then chances are the fan isn't operating. You could have a bad resistor pack (controls the speed) or a bad fan motor.