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1992 Suburban wont cool

Bill2 on Sat May 30, 2009 9:45 PM User is offline

Year: 1992
Make: chevy
Model: sububan
Engine Size: 454
Refrigerant Type: r134a
Ambient Temp: 90
Pressure Low: 32
Pressure High: 275
Country of Origin: United States

Looking for some help with a 92 suburban with front and rear ac. This truck has been converted to r134a. Truck has got a new ac compressor, rear evap, rear expansion valve, accumulator, condenser, manifold hose, and liquid line. Problem is I cant get this truck to cool below 50 degrees at center vent bringing engine rpm up to 2500. That is with ambient temps at 90 degrees and low pressure 32 high side 275. With rear unit turned on low side pressure climbs between 45 to 50 and high side 250. Rear unit only blows about 65 degrees at vent. Am I asking for to much after converting this unit. Vacuum was pulled with a robinair 6 cfm vacuum to 29in. New pump oil and vacuum for four hours with micron gauge to 270 microns. Old lines and front evap was flushed. 11oz of pag 150 was added to empty system. tried another compressor thinking suction side would not pull down enough with no change. Also when rear unit is running the pressure side is cool and liquid side is hot. Front evap temps are same from pressure side and liquid. Does the rear have a faulty new expansion valve? Why wont front ac unit blow any cooler when it runs by its self? System refrigerant capacity is 68oz I have tried everything from 40oz all the way to 68oz with not much change in temp. What am I missing? Is it possible to get this to cool better. I have been concerned with getting the low side pressure down in the 20 to 30 range to get a lower vent temp. Am I going in the wrong direction about this. Thanks

chris142 on Sun May 31, 2009 11:06 AM User is offline

I have had no luck with retrofitting Suburbans. I've tried different tubes, condensors, electric fans etc and an R12 Suburban just won't work well with R134a.

Bill2 on Sun May 31, 2009 12:14 PM User is offline

Bill2 on Sun May 31, 2009 12:18 PM User is offline

So does this sound like a typical situation for a suburban with r134 or could I get it any cooler with the r134. Thanks Bill

Cussboy on Sun May 31, 2009 1:07 PM User is offline

Spray some water over the condenser, see if that drops the temperature; I am wondering if you might have a weak fan clutch and less air is being drawn over the condenser than should be. I had an '88 dual-air Sub which I kept with R-12 when the compressor started leaking, and it cooled fine, in Arizona yet. And my current '94 Sub with factory R134a also cools nice.

Chris142 says his experience is that Suburbans don't do well with conversions to R134a, so maybe he knows a lot about this.

Bill2 on Mon June 01, 2009 8:43 PM User is offline

What was the coolest you could get one to get. I have even played with orifice tube size with not a lot of luck.

bohica2xo on Mon June 01, 2009 9:37 PM User is offline

What does it do at highway speeds?

Duct tape the gauge set to the windshield, and get some readings @ 50+ mph & 1500+ rpm. If it cools ok there, it is a condensor airflow issue.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

tamiii1 on Tue June 02, 2009 5:57 PM User is offline

I have an 85 Suburban with just front air and i did pretty much everything you did,all newunits with R134 and it would never go below 50 degrees,I tried a couple different otubes and clutch fan also.After about 2 years i tried another compressor but still did not get real cold,it did drip alot in humid weather though but would not keep me cool.I just bought some of this envirosafe R12 substitute but after reading some stuff about how unsafe it is I dont think i am going to use it now.I am no AC expert but i wasted alot of money and time over the last 5 years trying to make this truck AC work,but I think its time to give up.Hope you have better luck with yours...Maybe putting R12 back in it would work better since that was what it was made for.

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