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Compressor runs for 12 seconds

extramile on Thu May 21, 2009 8:10 AM User is offline

Year: 1990
Make: GMC
Model: Sierra
Engine Size: 305
Refrigerant Type: R134
Ambient Temp: 70
Country of Origin: Canada

Charged my own 1990 pickup yesterday, everything went good, system holds 2.5lbs of R-12 so I took 80% of that for 134( it was already converted ) Problem is when the compressor runs sometimes it will cycle for about 13 seconds then shutoff and start up again right away for a second or two. Doesn't do it every time though. Thought about clutch gap but it looks ok. I didn't ground the high pressure plug yet that plugs in the back of my R4 compressor as spoke about in previous posts. Air out of vents is about 50, not bad for a R12 to 134 but I didn't replace the evaporator which I should of but when I do my own AC it doesn't pay as well as doing a customers, lol.

mk378 on Thu May 21, 2009 10:12 AM User is offline

You need to watch the pressures as it cycles. It should be coming on at around 45 psi low side and off in the low 20's, while the high side stays under control. Unreliable cycling could be the low pressure switch or the clutch gap.

extramile on Thu May 21, 2009 10:13 AM User is offline


I grounded the high pressure switch plug that plugs into the back of the compressor, it seems to have stopped doing the above condition I described. Compressor stays on for about 7 seconds then shuts off for probably 12 to 15 seconds. When I was filling I had an issue with my scale so I know I have close to 2 lbs in but not exactly sure. My pipes are cold at compressor and and evaporator but no water coming out of evaporator. I am wondering if I am a tad bit low yet. I know I had water out of evaporator last year. The outlet tube for water out of evaporator is clean an not plugged, this and only 50 at vents has me thinking 1/4 to 1/2 lb low on freon.

Chick on Thu May 21, 2009 12:51 PM User is offlineView users profile

Water will only come out the drain on humid days..No humidity, no moisture to remove from the air.. Did you pull a deep vacuum before you charged? You do need the correct amount of refrigerant in the system to cool.. Hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

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