A/C Diagnostics

[StickyLifter]

Good Morning,

The A/C on my 1984 Sierra worked fine last summer, but isn't working this year. I checked for voltage at the compressor with the engine running and switches turned on, but found none. I looked for blown fuses and didn't find any. Is there a relay for the A/C system? Does anybody know of a good diagnostics source?

Thank you for your help!

John

 

[yevgenievich]

Check for 12v at the low pressure switch and verify it is closing. If pressure gets low, low pressure switch will disconnect power to the compressor

 

[StickyLifter]

Check for 12v at the low pressure switch and verify it is closing. If pressure gets low, low pressure switch will disconnect power to the compressor

Thank you! I'll check that out...

 

[Scott91370]

You can jump the wires on the switch (do not do it for more than a second or two) to see if that turns on the compressor. Could be low freon or bad switch.

 

[StickyLifter]

Thank you both for the suggestions. The problem turned out to be low refrigerant level. I had it in the back of my pea-brain that I had maybe screwed something up when I was messing around under the dash earlier this summer.

 

[Bextreme04]

Thank you both for the suggestions. The problem turned out to be low refrigerant level. I had it in the back of my pea-brain that I had maybe screwed something up when I was messing around under the dash earlier this summer.

Make sure you find where it is leaking from.. refrigerant doesn't just naturally leak out over time. I have a newer R134 switch on mine with a plastic body and it was leaking past the oring there. I unscrewed it and screwed it back on and the leak went away(mostly). I checked it with soap and it was still a very slow leak, so I pulled it and put a second oring on it(that seamed to stop it finally)