Constant interior heat

[tksoldierx]

Howdy,

95 K1500 Silverado trim, A/C doesn’t work because of the A/C pump clutch failed. This wouldn’t be so bad but the vents are constantly spitting out hot air out.

Even if the HVAC controls are set to OFF+COLD+any combo of defrost/top vents/bottom vents. Nothin comes out when you first turn it on, but after driving for 5-10mins you can feel that all the vents are warm, and if you drive it for long enough you’ll have to roll the windows down to dump the heat out even during a literal blizzard.

All the blend doors I can see work exactly how they should, and look intact. Engine temp has been 210 or under except for the rare occasional overheating while towing too much, so it shouldn’t be engine bay heat dumping out into the cab (right?)

It didn’t do this 3 years ago, I believe it started after it had to sit for a few months while I saved up for a new tranny. Any ideas as to the reason the vents get so hot?

 

[Schurkey]

1. Failed actuator(s)
2. Failed seals on the air door(s)
3. Failed control head

Does the actuator for temp control make noise when shifting from "hot" to "cold" and back? That could verify the control head and the actuator, assuming it's not so noisy as to indicate broken/stripped internal gears on the actuator.

I know a guy with an S10 that has failed seals on the air doors. I don't know if GMT400s are built the same way--metal or hard-plastic air doors with a rubber seal around the outer edge.

 

[Erik the Awful]

If the blend door motor is working, either your blend door shaft is dorked, or the seal is shot.

 

[tksoldierx]

1. Failed actuator(s)
2. Failed seals on the air door(s)
3. Failed control head

Does the actuator for temp control make noise when shifting from "hot" to "cold" and back? That could verify the control head and the actuator, assuming it's not so noisy as to indicate broken/stripped internal gears on the actuator.

I know a guy with an S10 that has failed seals on the air doors. I don't know if GMT400s are built the same way--metal or hard-plastic air doors with a rubber seal around the outer edge.

I took a listen this morning with the engine off and I can hear it whirring from hot to cold and back. Could be the seals

If the blend door motor is working, either your blend door shaft is dorked, or the seal is shot.

The blend door motor works, if I stick my phone under the floor vents at the right angle I can video that blend door turning to all the right positions as I change it with the knob, so at least that door shaft works

Sounds like it probably be the seals then. Do they sell the seals separate or do I have to get whole new blend doors to have new seals?

 

[Schurkey]

I have no idea, except that knowing GM, it's all discontinued and you'll have to fabricate something, or find a good one at the Treasure Yard.

 

[AK49BWL]

The doors are all plastic with rubber edges for all 400s. The main blend door and the upper two doors (which come in a housing as a unit) are available on Amazon, possibly RockAuto. The recirculation and temperature doors ARE NOT available anywhere that I've been able to find.

 

[Erik the Awful]

The blend door motor works, if I stick my phone under the floor vents at the right angle I can video that blend door turning to all the right positions as I change it with the knob, so at least that door shaft works

The blend door and mode door are two separate doors. The blend door controls your mix of hot and cold air. The mode door is the one that changes which vent the air comes out of.