88-94 5.7 Suburban A/C Diagnosis and Tuning

[L31MaxExpress]

Basic Auto Air Conditioning Compressor Facts - Vintage Air

The Basics Air Conditioning Theory The Basics Compressor Facts The Basics Safety Switches Basic Auto Air Conditioning Compressor Facts The next most critical part of an air conditioning system in […]

www.vintageair.com

alot of sights say they are far more efficient at above 1000 rpm

Compressors always move more refrigerant and BTUs the faster you spin them up to a point. Its a function of increased pumping capacity. That being said I have 1.5x the evaporator capacity of your system and I am still getting acceptable cooling at low rpm in much hotter ambients. That tells me that the compressor capacity at low rpm is not your issue unless something is wrong with that particular unit. What sticks out like a sore thumb to me is ~60 oz in a system designed for 36 oz. The compressor/condenser change and minimal change in hose length if any will not require nearly as much additional refrigerant as my vans system increased with the long hoses to the rear and rear evaporator added to my system. 60oz is only 8oz less than my van calls for on R134a with rear ac.

Personally I would recover the system, add 36 oz and see where that gets you. I think it will get you cooling a lot better. A factory GM front only R134a system in 94-95 calls for 2.25 lbs or 36oz. You have ~3.75 lbs stuffed into a system that calls for 2.25 lbs when it was factory. I would never expect that to cool well.

 

[L31MaxExpress]

well that means my truck is idling at 510 rpm i have never been able to get my idle up its always real low new iac and calibrate it and it always idles down way low i need to hook up a tach and see what its doing

500-525 is usually the commanded idle in a TBI. You can up the commanded idle in the chip a bit.

 

[cjcb1100]

if it was too much with a smaller orifice tube wouldnt my high side be through the roof like 450 psi or so ?
i have 2 sets of guages both read with in a few psi of each other

 

[cjcb1100]

i dont have the stuff to measure the temp on the lines and i dont understand how to even charge that way i have watched video just dosnt click to me i have always used the pressure chart i know thats not the correct way but it has always worked for me,

 

[cjcb1100]

also i drained the compressor and put 4 oz in the pump fill hole and 4 in the dryer

 

[L31MaxExpress]

if it was too much with a smaller orifice tube wouldnt my high side be through the roof like 450 psi or so ?
i have 2 sets of guages both read with in a few psi of each other

Just because it is overcharged, does not mean the pressures will be through the roof. The smaller orifice tube cause more liquid to condense into the condenser.

 

[cjcb1100]

well when i had 3 24oz cans in it my low side was super low like 14 psi

 

[L31MaxExpress]

i dont have the stuff to measure the temp on the lines and i dont understand how to even charge that way i have watched video just dosnt click to me i have always used the pressure chart i know thats not the correct way but it has always worked for me,

Honestly you do not even need temperature stuff. I did it for years with my finger tips. The sense of touch in your fingers should get you close. When you are getting close the line coming into the accumulator off the evaporator will get cold. The accumulator will still be warm. As you continue to slowly charge, the shell of the accumulator will get cold, followed by the suction line to the compressor. I stop charging when the suction line feels similar to the liquid line going into the evaporator past the orifice tube.

 

[cjcb1100]

think im just gona admit defeat nothing i do helps and ive sunk 1000 bucks into this and never got below 60 f at idle on a hot day o well thanks for the help

 

[cjcb1100]

all my lines get frosty when driving and condensate while sitting i know my blend door is working i replaced the foam and i took the actuator off and operated to cold manually this morning at 75 ambient i had 38 degree air i have 4 pushers on the condensor as well