Automotive Air Conditioning Information Forum (Archives)

nlt99 on Sun July 11, 2010 1:02 PM

Year: 2003
Make: Buick
Model: Rendezvous
Engine Size: 3.4L
Refrigerant Type: R134A
Ambient Temp: 92
Pressure Low: 17
Pressure High: 400+
Country of Origin: United States

Hi!
Sitting stopped at idle, when it's very hot outside (110-115 degrees), my compressor shuts off causing no cooling at stop lights. I checked the system yesterday when ambient was about 92 degrees, 42% humidity. Static pressure before starting was about 100 lbs both sides.

Test set-up (per factory specifications):

- A/C on
- Maximum blower speed
- Recirculation mode
- Panel-only mode
- Coldest temperature setting
- All vent outlets open
- Driver window open 5-6 inches


Results:

RPM........ Lo-side press...... Hi-side press....... Vent temp

Idle............... 34............................ 200................ 48 degrees
1500............. 25............................ 235................ 47 degrees
2000............. 18............................ 305................ 45 degrees
2500............. 15............................ 400................ 44 degrees
3000.............................................. 415 (compressor cut-off)

- Engine temperature was normal at all times
- Both cooling fans were running at high-speed (12v across both) at all times
- As soon as the car is put in motion the A/C works normally
- Condenser and radiator are clean (no obstructions)

The factory service manual procedures only test at idle and my results (including static pressure) fell within the spec's given for the ambient conditions

The only thing I question is that the condenser sits about 1" in front of the radiator. The cooling fan asm is sealed against the back side of the radiator, but there is no seal between the condenser and the front of the radiator. I haven't been able to compare to another Rendezvous to see if this is normal. I know the front end of this car was repaired before I bought it due to a front-end collision and I don't know if they assembled everything correctly. Is it normal to have that large a gap between the front of the radiator and back of the condenser with no seal?? Seems like air can easily be drawn in from the sides instead of forcing it to go through the condenser coils.

Seems to me that the high-side pressure goes too high, and the low side-pressure goes to low at the higher RPMS, but I can't find any spec's other than the factory manual which only shows idle spec's

Any suggestions or info would be greatly appreciated!

Thank you! Nick


Edited: Sun July 11, 2010 at 1:16 PM by nlt99

mk378 on Sun July 11, 2010 6:10 PM

Also consider improper service: overcharged with refrigerant or oil, or air in the system from not pulling a vacuum after repairs, or a knock-off replacement condenser was installed that doesn't have OEM performance.

nlt99 on Mon July 12, 2010 2:39 PM

Thanks for your suggestions!!

If it was overcharged with refrigerant, wouldn't my pressures be different than factory spec's at idle (they're not)?

Not sure how to tell about excess oil... do you have any suggestions other than a complete evacuation and refill from scratch? (ugh!)

Will try to determine if condenser is OEM or not by comparing to another Rendezvous

Air in the system was one of my concerns.... would that act this way: normal at low RPMs and higher-than-normal at higher RPMs??

Do you happen to know if the condenser is normally spaced away from the front of the radiator with no seal in between??

Thanks again for your help! Nick