HVAC help

[TommyD11730]

Ok Guys maybe someone can help me, or maybe I don't have a problem at all.
My 1991 K5 with factory air blows weakly through the defroster ducts. When in defrost mode it's also blowing out of the AC dash vents. So I close those vents to try and increase airflow out the defrost.
Checking all functions Infact it always blows out the AC vent. Heat would be Floor (heat) and AC vents. AC would be just the AC vent and Defrost is Defrost/vent.
So is this normal? When I change functions I see 3 vacuum motors under the dash operating doors. Is their a 4th motor I should be looking for to check operation?
Thanks Guys!

 

[paratrooper307]

One thing you can do is check the ducting and make sure it is secure and not leaking air out under the dash. Another is to check operation of the blend door. Mine blows most strongly out of the floor, and the A/C blows stronger than the heat out of the dash vents. It sounds like your actuators are working properly. The dash blows weakly, but the truck can still get uncomfortably warm inside when it gets going, so I just roll with it.

 

[TommyD11730]

It just seems odd that it's always blowing out of the AC vents as well as any other selection I make. Tomorrow I'll get under the dash, something's not right.

 

[blazer74]

Sounds like your blend door is not closing all the way.
Take the front cover off that's just to the right of center of and partially under the dash on the heater box. 2 screws at the bottom and 1 at the top.
Look to see if the door is closing all the way when you select heat or defrost.
Possible it has a broken clip on the
door .

 

[6872xtc]

What he said...... I have fixed the problem with making small metal tabs. But also check that you are getting good vacuum to the control. Can you hear the vacuum noise when you move the lever? Mine had a rotten section of line up above the distributor.

 

[TommyD11730]

Sounds like your blend door is not closing all the way.
Take the front cover off that's just to the right of center of and partially under the dash on the heater box. 2 screws at the bottom and 1 at the top.
Look to see if the door is closing all the way when you select heat or defrost.
Possible it has a broken clip on the
door .

BOOM!

Now to see if I can locate the clip!

 

[6872xtc]

That's the one that I have replaced with metal tabs going vertically. If you search around on the forums, you can find information on replacements and what guys have done.

 

[TommyD11730]

That's the one that I have replaced with metal tabs going vertically. If you search around on the forums, you can find information on replacements and what guys have done.

I lamed out and ordered a few from my dealer. If anyone needs one, hit me up, my treat.

 

[blazer74]

Throw the part number out there to help others if needed.

 

[TommyD11730]

Throw the part number out there to help others if needed.

3018715