I have a 2000 2500 4X4. I need a little help troubleshooting a heater problem. With the A/C or vent turned to full cold I get hot air when sitting at a stop light with the brakes applied. I can get the heater to cold again by turning the control to off and then back to A/C or vent but the next time I brake the heat comes back. Any ideas on how to fix this?

Thanks
Jeff

 

Could it be a vacuum leak causing the blend door to move? Have you checked the rubber vacuum tubing in the engine compartment? Also the plastic tubing.

 

The blend door on the 2000 is controlled via an electric motor. Only the recirculate door and the vent position are controlled with vacuum.

So if you turn the system to off, then back on while you are stopped everything works normally again till the next time you hit the brakes?

How hot is the air coming out? Similar to the heater being on full hot, or just ambient temp from the outside air?

 

Hows this..... vacuum leak somewhere when braking causes the vacuum to bleed off on the recirc door allowing air in from the engine compartment if the seal is missing from the firewall to hood that air would be very hot and would overpower the evaporator. Make sure your recirc door works and that seal is in place.

 

The onyl time I can have the system turn back on to normal is to turn the A/c off, then let off brakes and turn back on.

 

2000 has hydro boost brake,not vacuam.

 

so where should i look?

 

So is the air that is coming out just ambient temp warm or hot like the heater is on full and the air is coming across the heater core?

 

I cant tell cause its 105 outside

 

Ouch, I know how that feels.

So if you're not on A/C, just on Vent, will it get hotter when you stop? Or does it just happen on A/C?

Trying to figure out if it might be something electrical kicking the compressor out. Do you hear the A/C compressor start/stop at all when you come to a stop?

 

It happens on A/C or even just on Fan. I can def hear a POP.

 

AH! didn't look it up and if it does it even on vent or just AC not Max then the recirc door is out of the picture. Check the hood seal anyway it makes a difference. There should be a rubber piece that runs across the top of the fire wall, there should also be an "L" (6X9in) shaped piece of foam about one inch square on each side. It's the foam that goes missing, along with the rubber coming off. Is the engine coolant full? If not it could be partially emptying the heater core when revving but allows it to refill at idle.

If it does it on vent... It's not an AC problem. So either the blend door is wandering away, could be the rotary actuator has broken. Remove the blend door actuator and see what you have, or the heater core is not full all the time.

 

How do i remove the blend door actuator?

 

Could it be that when you stop you don't have any air flowing across the condensor and it gets too hot? Maybe low on freon? Just a few WAG's.

 

The blend door act is located up against the hump on the pax side. It is the only electric actuator in the system and is held onto the heater plenum by three screws that are difficult to get without removing the plenum but not impossible. Check your engine coolant first.

Again... if it does it in vent mode it's not an AC or recirc door problem.