A/C Compressor not kicking in..

[thacheetah11]

Just bought my 1984 k10... PO said the A/C worked but needed freon. It's been swapped over to 134 already. I put freon in it but nothing... The compressor isn't coming on. Trying to eliminate everything else besides bad compressor.... Thanks


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[smoothandlow84]

You'll have to run a jumper wire across the ac pressure switch. If the 134 level is too low, the compressor won't turn on and draw in the oil. That system usually will take 3-1/2 cans of r134 when its empty. I ran a jumper on my ac pressure switch to activate the new compressor (make sure you add the required amount of oil to the new compressor first) prior to charging the system or damage may result. Once the first 2 can of r134 were drawn into the system, I was able to disconnect the jumper wire and finish up the charge.

 

[thacheetah11]

Thanks for the advice! Now it's kicking in and cooling!


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[smoothandlow84]

Thanks for the advice! Now it's kicking in and cooling!


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No problem....glad I could help.

 

[moorevisual]

No problem....glad I could help.

since you sound like you know your stuff, maybe you can help me with my issue...

My compressor keeps clicking on and off, but it only happens once I get to about 2000-2500 rpms, and no matter what I charge it up to (I've tried 35, 40, 45, 55 psi), it continues to to cycle on and off every 5 seconds or so. When I have the gauge on it, I can watch it drop as the RPMs increase and as soon as it drops below 25 psi (into the white on the gauge) the cycling starts.


BTW - when I got the truck the compressor was dead, so I've put on a new compressor, dryer, evaporator, orifice tube, flushed and vacuumed the system, and charged with 134.

Someone mentioned to me that maybe the pressure switch should be changed to one with a lower cut off, since 134 runs at a lower pressure that r12? But others I've spoken with said it should work fine with the original switch.

Any advice?

 

[smoothandlow84]

Im leaning towards replacing the pressure switch, it could have a short or bad connection. I would replace it with an oem unit first, rather than something different. When I installed and charged my ac unit, I also replaced the oem pressure switch just to be on the safe side since it wasn't an expensive part. At 30 plus years of service, I figured why not replace it along with everything else. The r134 doesn't work nearly as efficient as the r12, but then again, at $45 per can of r12 (if you can source it) is beyond rediculous. I can still source it locally here in Phx, but not willing to pay 10 times what it's worth.

fwiw..a full charge with a new compressor, accumulator, hoses etc, should be close to 4 cans for a full charge.

My system was gutted by the p.o. and everything except my condenser was replaced.

 

[moorevisual]

Im leaning towards replacing the pressure switch, it could have a short or bad connection. I would replace it with an oem unit first, rather than something different. When I installed and charged my ac unit, I also replaced the oem pressure switch just to be on the safe side since it wasn't an expensive part. At 30 plus years of service, I figured why not replace it along with everything else. The r134 doesn't work nearly as efficient as the r12, but then again, at $45 per can of r12 (if you can source it) is beyond rediculous. I can still source it locally here in Phx, but not willing to pay 10 times what it's worth.

fwiw..a full charge with a new compressor, accumulator, hoses etc, should be close to 4 cans for a full charge.

My system was gutted by the p.o. and everything except my condenser was replaced.

thanks, i will be trying that here in the next few days

 

[moorevisual]

Im leaning towards replacing the pressure switch, it could have a short or bad connection. I would replace it with an oem unit first, rather than something different. When I installed and charged my ac unit, I also replaced the oem pressure switch just to be on the safe side since it wasn't an expensive part. At 30 plus years of service, I figured why not replace it along with everything else. The r134 doesn't work nearly as efficient as the r12, but then again, at $45 per can of r12 (if you can source it) is beyond rediculous. I can still source it locally here in Phx, but not willing to pay 10 times what it's worth.

fwiw..a full charge with a new compressor, accumulator, hoses etc, should be close to 4 cans for a full charge.

My system was gutted by the p.o. and everything except my condenser was replaced.

One thing - I noticed when I went to check the part at Oreillys, the description of the switch states that it cuts off at 29psi, and on at 30psi, which is exactly what mine is doing now. I guess the proper question I should be asking is what would make my psi drop below 30 at just 2000 RPMs?