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Low Side-high reading / High Side-low reading

ykf7b0 on Fri June 19, 2015 12:01 AM User is offline

Year: 1976
Make: Chevrolet
Model: Corvette
Engine Size: 350
Refrigerant Type: R134a
Ambient Temp: 90
Pressure Low: 80
Pressure High: 80
Country of Origin: United States

I'm trying to get the a/c up and going on my wife's 76 Corvette. The system has been converted to R134a. I have replaced evaporator, new desiccant, total flush, and lengthy vacuum and leak check. The A6 compressor clutch is engaging but the pressure has equalized with a low high side reading of 80 and a high low side reading of 80. Has my compressor gave up?

TRB on Fri June 19, 2015 11:12 AM User is offlineView users profile

With compressor engaged and equal pressure. It is a good chance your compressor is not working correctly if fully charged.


When considering your next auto A/C purchase, please consider the site that supports you:

ykf7b0 on Fri June 19, 2015 3:24 PM User is offline

I don't have it fully charged. I couldn't get any more refrigerant to draw in other than 16 oz. What's going on with it? Thanks!

GM Tech on Fri June 19, 2015 3:40 PM User is offline

Did you close your valves on your gage set when taking the readings? Otherwise you are bypassing the system and pumping thru your gage.

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......

ykf7b0 on Fri June 19, 2015 7:55 PM User is offline

I don't think I understand you correctly. I have the low pressure guage valve open when charging and high pressure gauge valve closed. I have the coupler valves open on both high and low charging ports. My readings are obtained through this proceedure. Please explain. Thanks!!!

Jag987 on Sat June 20, 2015 3:25 AM User is offline

If the couplers that attach to the car at the ends of the hoses have manual valves on them, they need to be open. The knobs/valves on the manifold next to the gauges need to be closed.

I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

ykf7b0 on Sat June 20, 2015 10:16 AM User is offline

Both manual couplers are open and Low side gauge valve is open to ingest refrigerant - correct? To get readings both Low and High side manifold gauges are closed - correct? If so, my pressure readings are always end up equal (80 psi) on both gauges and I cannot get the compressor to draw in any more refrigerant than the 16 ounces that it has taken in. Compressor clutch is engaged.

Crude dude on Sun June 21, 2015 4:51 AM User is offline

Wonder if there is an issue with the orifice tube or expansion valve. Sounds like no flow control.

ykf7b0 on Sun June 21, 2015 9:16 AM User is offline

It could be that and I hope it is not. I have a factory VIR.

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