Automotive Air Conditioning Information Forum (Archives)

rn1255 on Wed May 14, 2014 7:24 PM

Year: 1999
Make: Chevrolet
Model: Suburban
Engine Size: 350
Refrigerant Type: R134A
Ambient Temp: 80
Pressure Low: 35
Pressure High: Unknown
Country of Origin: United States

Hello all: I'm having some very frustrating problems fixing my A/C. The system is properly charged, orifice tube replaced, and blend door motor replaced (I verified it's operation prior to putting it back together). The problem is the front a/c blows 20 or so degrees warmer than the rear. The rear blows in the upper 40's, and the front in the upper 60's. If I overcharge the system, I can get the front down to 58 or so, but then the rear blows warm. There is no cabin filter, as I have checked that already. I'm at wits end here. Anyone have any ideas?
Thank you in advance. Bob.

-------------------------
Bob Niehaus

Dougflas on Wed May 14, 2014 8:39 PM

Try clamping off the heater core

GM Tech on Wed May 14, 2014 9:15 PM

Got "recirc" selected on the front? the rear is always on recirc- so to be fair.......

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

rn1255 on Thu May 15, 2014 12:47 PM

I tried that, no help.

-------------------------
Bob Niehaus

sdflyer on Thu May 15, 2014 5:06 PM

Bob.

1. how do you know "the system is properly charged"?
2. replaced blend-door-motor, have you verified correct position (forget whether it works) mine moved, but were not in the right position
3. what do you mean "if I overcharge the system..." how do you measure what you add/remove? weight?
4. have you tried "under-charging". if the evap is flooding "too much" you may not be getting enough cooling.
5. why is your High-Pressure "unknown"

and *most importantly* did you replace the orifice with the correct size???

front evap uses orifice tube, rear evap uses TXV... i am guessing if the incorrect orifice is used, the front evap will not operate correctly.




Edited: Thu May 15, 2014 at 5:07 PM by sdflyer