When the AC is on and I stop at a light, when the light changes and the truck is accelerating the air gets hot!

Any comments would be appreciated!

Thanks,

mtngirl

 

The blend door that controls where the air comes from and where it goes is operated by engine vacum. on acceleraton engine vac. drops momentarily and would disrupt the vac signal to the HVAC system. Have the truck inspected for a leac in the vac. system.

 

I will have someone look at the vac system or try and do it myself!

mtngirl

 

Actually the blend door is not operated by vacuum. It has a electric actuator that moves it. Sounds like you have a broken blend door. When you accellerate the door moves back to let the air go through the heater core, when you brake, the door goes back in the other direction and closes off the heater core.

 

With less airflow through the condenser (at a traffic light), the R134 system does not cool as well. If the temp cools off after you get moving that would tell me the system works, it's just inefficient.

You may ask an ac shop if they can do something to "supercharge" the system to increase cooling at lights.

Electric fans may do the trick as they are on whenever the ac switch is on Max; that would increase airflow and cooling, but would be the expensive way to chill for a 2-minute light.

 

In all my years of performing A/C repair, that's the first I've heard of that. When I test A/C operation, I always test the discharge temps with the engine idling. If it gets warmer than 50 degrees then the system is not operating properly. And there is no supercharging the a/c. If you overcharge it, it will not work properly. It can cause the compressor to fail, or even cause the evaporator to freeze.

 

I apologize if I was misleading the discussion. Albeit an old source (1994), http://yarchive.net/ac/politics.html discusses shortcomings of R-134. I'm not sure if too many things have changed since the article was written; my ac still gets "warmer" in traffic during the summer.

Also, I would not intentionally recommend someone overcharge their ac system. There is one product, Sub-Zero, that adversises increases in efficiency or temp reduction by 18%. The can does have R-134 (14 oz) and "ac synthetic" (2oz) and would require the evacuaction of the proper amount to avoid overcharging the system. Use of a product like Sub-Zero is what I meant when I stated "supercharge" the system.

Again, my apology.

Curt