I'm working on a Nissan Sentra, R134a system.

The A/C doesn't blow cold.
The compressor clutch engages in a/c mode, and never cycles, just stays on all the time.

I bought a can to top it off, the system will not pull any in. I tried every angle, shaking it, waiting, waiting, but it will not pull it in on the low side. The dummy guage on the can reads low if the a/c is running. Of course, it goes way up if I shut the a/c off, as the system pressure equalizes.

I'm wondering if I've got a defective can, but this stuff is $30 so I don't want to buy more just for fun.

The car had a front end collision a few years ago that may have damaged the condenser, and the A/C hasn't blown cold since then.

If compressor is constantly running, that usually indicates sufficient charge (on a GM anyway).

You do have the engine running, can upside down and shaking, and valve open while you're trying to down-load refrigerant, correct?

Yes! I also tied my shoes and washed my hands.


If the system had a proper charge I'd expect the compressor to cycle based on pressure, not run constantly.

Oh, and the lines get barely cold, but not like they should.

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Doesn't seem right. Usually compressors won't engage with low refrigerant.

Does this system have a "Max" position selection that the compressor is always running?

Can you releave any pressure out of the low side?

A lot of pressure on the low side could indicate the orifice screen may be blocked/plugged, or the pressure sensor on the low side tube close to the condenser is hosed.

The compressor will run with a minimum charge on most GM cars. I don't know if this is true of Nissan. But if it was a GM car, I would say if its not blowing cold, and the compressor is running, your probably at about 75%. You can try the hot water method. Dangerous if your not careful, but I do it all the time. Get a small bucket of hot water (sink hot, not stove hot). Put the can in the water so its 50% covered. Give it a couple of minutes to warm up, and then turn the valve to open it up. Should cause a higher pressure in the can forcing out the refrigerant into the already pressurized system. Good Luck,

DG

Are you using a manifold gauge set... you might want to see if the high and low side pressures are balancing....

DG

No, my guage set only works on R22.

That would be easy otherwise. On my vette awhile back those guages indicated the condensor actually plugged and prevented charging it, but I was able to clean it out.

I wonder if the condensor was damaged in the crash. Those are usually pretty cheap.