No Defrost

[84GMCSierra]

Good Afternoon members. I have a question concerning my defrost not working on my 84 C2500. I'm wanting to know if this little "pot" could be the culprit? The defrost worked for a couple years then went screwy and quit working, but the regular heat works just fine. The "Defroster Actuator" is what I'm referring to under the dash on the side of the box assembly. Can these be replaced, or could it be in my switch panel? Any and all help will be greatly appreciated. Thanks

 

[75gmck25]

You can use a hand vacuum pump to pull vacuum on the actuator and see if it works. If it still works, then it’s probably the lines to the controls.

Do the rest of the actuators work when you change hvac positions. For example, if you put it in max a/c you should see the flap open in the passenger side footwell, to go to recirculate.

 

[84GMCSierra]

I took the AC out in 2019 when I bought the truck so not sure about that part. I will check the rest of the positions though. Thanks

 

[WFO]

Do you have vacuum to the actuator?

 

[84GMCSierra]

Do you have vacuum to the actuator?

Probably not but will check. know the line that goes in the firewall on the right side keeps coming apart. It was broken so I tried a piece of 1/4" tubing over it to connect the 2 pieces. I'll try to get a pic. Not sure if it'd the line for the defrost or what.

 

[PrairieDrifter]

Probably not but will check. know the line that goes in the firewall on the right side keeps coming apart. It was broken so I tried a piece of 1/4" tubing over it to connect the 2 pieces. I'll try to get a pic. Not sure if it'd the line for the defrost or what.

That line is the main vacuum supply for the hvac. You need to make sure that's proper.

 

[neiltee]

If you are looking for replacement parts try "Old Air Products"