97 Park Ave A/C
 

The repair shop owner is telling me that the driver's side A/C is not blowing cold because there are two Freon circuits (and I guess two evaporators) and the one side is leaking freon.
This makes no sense to me. I was thinking it was a blending door malfunction.
I've never heard of a car having two evaporators (i.e. two independent systems).
Am I crazy or is the shop owner?

I'm gonna say the shop owner. Even if he was right, even if it did have 2 evaporators, and onewas leaking, it wouldnt cause one side to act like that. There is actually a quarter of the pressure running as there is on that side than when turned off. If there was a leak, it would leak continuously until the pressure is too low, and the computer will refuse to fire the compressor. If the compressor continued to run it would self destruct.

Based on the design of the system however, i have heard that that could be a sign of low refridgerent, but it would go away when the system is properly charged.

Again tjis is assuming you do not have blend door actuator issues

The two circuits may be considered the high / low = on the pressure side.
One evaporator/Condensor.
If you set the PA temp selector to 60 F and push the Auto button as well the compressor clutch should engage.
If it does not engage it generally is that you have a leak and have insufficient refrigerant.
If the clutch does engage the accumulator should get very cold quickly.
https://www.gmforum.com/attachment.p...ine=1401689807
If you want a good read just google:
"Auto air conditioner blowing warm air not cooling"
Hope this helps !

i have seen vehicles with two evaporators but never two circuits, the same everything else is used but in bigger vehicles like my yukon they have a second evap and fan in the back. never have seen two side by side or in a car, doesnt make any sense.

dont take your car to this shop anymore, see if your pressure is good and blend doors are operating

Thanks to all for the great info.

These internet automotive forums are priceless! I know they have saved me a lot of time and a lot of dollars.

There is only one evaporator........however there are two duct passages....one for the left side and one for the right,,,,,one side will use the upper half of the evaporator and the other side will use the lower half........

If the temp doors for each side is working correctly(this can be verified by turning the A/C system off(vent mode or ECON), and commanding both sides hot and both sides cold....if the output temps are the same, the actuators are working.......

Then the usual culprit, is low freon.....if low, the best way to describe it is, the freon will short circuit though either the upper or lower half of the evaporator(depending on where the inlet/outlet is to the evaporator)....thus one half of the evap will be cold and the other half will be less cool or warm.....causing the disparity in temp from one side to the other....

Thanks Tech II
 

Great explanation and it all makes perfect sense.

Thanks

I spent most of last summer fussing with my PA ac system. There is a programmer that ( small computer) that oversee the entire system, two actuators that open and close separate blend doors to give separate temps for passenger side and driver side. The main control panel and the passenger side temp adjuster (makes the pass side about 5 degrees cooler or warmer depending on how you set it). There are sunlight sensors cabin temp sensors exterior ambient temp sensors and who knows what else. Long story short the Dealer can hook up his scan tool and give you a printed read out on how each of these things is performing in about 10 minutes. He diagnosed and fixed in 10 minutes what I had been trying to fix for three months. Best 100 bucks I ever spent!!! I fix them myself all the time but, sometimes it is best to get some help.