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High side low

jameshobbs on Tue June 29, 2010 9:57 PM User is offline

Year: 1995
Make: Chev
Model: C-10 Pick-up
Engine Size: 2.2
Refrigerant Type: 134-A
Ambient Temp: 90
Pressure Low: 28
Pressure High: 100-120
Country of Origin: United States

Help Please
Last year my pastor brought his truck to be and it was bone dry thought it was a belly leaking V5 put dye in found crack in pipe around muffler. Got muffler/ hose assay. from Tim plus new Accumulator / drier, O-ring kit new (White) O-tube replaced all that stuff pumped down 2 hours held it for 30 min. charged up 28 ish low side 200- 225 high side cooled great. ( Life was good)
Got it back today dry again looked like service ports maybe leaking screwed new one in low side, high side had a funky screw-in ball valve deal got new one for14.00 bucks at Chevy. dealer vacuum down 2 hours held for 30 min.(per tag holds 1 lb 14 oz ) added first pound low side 30ish high 50-60 ( 92 degree & 80+ humidity day) acted like it did not want to take last 14 oz of 134a. Low side 28 High 100 and bouncing slowly to 125 max needless to say not cooling. felt line before O-tube ( evaporator side) it was warm about half way back to condenser it felt a little cool were it should be hot.
Thought maybe there was trash in the O-tube pulled old one looked good installed new( white) one pumped down charged up same thing
28 low side 100-115 high side maybe bouncing slowly to 125 max no cooling. I would think the high side should be 225 to 250 on a 90+ day like this any ideas why high side is low ?

-------------------------
Life is not measured by the number of breaths we take - but by the moments that take our breath away
Thanks, Randy

GM Tech on Wed June 30, 2010 8:21 AM User is offline

Put the proper charge amount in it----then report pressures-- your current pressures look as if you are undercharged--

Is cooling fan clutch fan engaging properly? Your suction pressure says you have a good pump- it is low enough to get all the refrigerant in-- add a few ounces extra to account for any losses you have experienced while changing hoses etc.

Must be an S-10 pickup truck if you have a 4 cylinder engine--- a C-10 is a full sized pick-up with an R-4 compressor back in '94

-------------------------
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......

Edited: Wed June 30, 2010 at 8:23 AM by GM Tech

mk378 on Wed June 30, 2010 9:09 AM User is offline

True, you need a full charge first to diagnose a variable compressor system. It looks like there could be a blockage somewhere between the compressor and high side port. Make sure you don't have an extra o-tube at the condenser outlet.

GM Tech on Wed June 30, 2010 10:16 AM User is offline

Condenser outlet OT only apply to full sized pick-ups which the OP has yet to confirm-- I'm guessing he has an S-10- with the 4 cylinder engine and a V-5 compmressor.

Now if he has a C/K truck, then he can't have a 4 cylinder engine, only a 4.3L or a 5.7L- both which would be R-4 compressors...

So only the OP can enlighten us--- crystal ball is dirty......

-------------------------
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......

jameshobbs on Thu July 01, 2010 9:53 PM User is offline

Your right guys it is a S-10 with a 2.2 4 banger. Sorry ! I am charging with a 30 lb tank and per my scale it weighs 25lb after putting 30 oz's in this truck. I kept thinking it was low too. so I would crank the low side of my gauge set ( the center line is hooked to the tank) open and the low side would jump from 28 to 90ish PSI but the high side will not rise past 110-120 max! Close the low side valve and low side drops to 28 again it is almost like it does not want ( will not take) any more 134-A?

Thanks so much for you in put guys !

-------------------------
Life is not measured by the number of breaths we take - but by the moments that take our breath away
Thanks, Randy

mk378 on Fri July 02, 2010 12:01 AM User is offline

It's normal for low side gauge to go up like that. You're measuring pressure from the tank then. When you close the valve it's measuring pressure in the car again. Just leave the valve open and let it flow in.

The proper way to charge with a 30 is to weigh the tank constantly during charging and watch until its weight has decreased by the specified charge weight. Prop the hose real still so that changes in the force on the hose don't affect the result.

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