Car a/c: suction pressure not changing when compressor kicks in

[oldag]

A/C not cooling.

Car off. Hook up gauges. Both suction and discharge pressures reading the same, as expected.

Turn car and a/c on. Discharge pressure gradually rises to about 210 psi. Suction pressure does not change, stays at about 65 psi.

I have not seen this before. Any ideas?

 

[TexMex247]

Probably don't have the valve open enough. Almost impossible to make pressure only

 

[TexMex247]

I'd pop off the low side port and pop it back on, then slowly open it till the pressure changes. You can also let it flow through the gauge block to make sure it is open. With 200 on the high side, close both ports, open valves on gauge and let freon migrate through gauges to the low side. If pressure doesn't rise then gauge is defective. Then slowly open low side and pressure should equalize.

 

[oldag]

Will try again. The suction gauge did drop to zero after I released the freon in the hose (after removing the hose from the pressure port, of course).

 

[oldag]

You nailed it. Something has gone screwy with the gauge set. Third time was a charm.

Thanks.

I was just not able to imagine how the discharge could be ok but the suction not changing.

 

[TexMex247]

Glad it worked out.

 

[TexMex247]

Is it cooling ok. 220 ish seems fine for the high side pressure with a mechanical fan system. Tad high if it has an electric fan.

 

[oldag]

Cooling okay. Pressure read lower after hooking gauges up a second time. Got to thinking back, and the gauges were probably 35 years old.

New gauge set on order.

 

[Younggun]

Online there are some good charts for typical pressures at a given ambient temp.


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