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AC Compressor Bypass

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Old Aug 15, 2007 | 09:43 PM
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Default AC Compressor Bypass

How do you start the compressor if the pressure is too low and you have to bypass the low pressure safety?
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Old Aug 16, 2007 | 08:17 AM
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I've had good luck with late model GM's just disconnecting the batt cable for a minute. Never tried it with my C5 tho..............
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Old Aug 19, 2007 | 01:03 PM
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Is there any other way to basically force the compressor to start up?
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Old Aug 19, 2007 | 01:33 PM
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Originally Posted by waterzap
Is there any other way to basically force the compressor to start up?
Why would you want to force it .... the PCM (it controls the compressor clutch) is programmed to "protect" the compressor if the refrigerant pressure is too low or too high (OK range between 30 psi and 410 psi). The refrigerant has a lubricating oil that lubricates the compressor. If you have no refrigerant then you have no oil.

Power for the clutch is provided by the Underhood Fuse Block (Fuse 24) and then the A/C Clutch relay (Relay 34) also located in the UH Fuse Block. Power flows from the relay to the Clutch diode via a DARK GREEN wire, and the Ground is the BLACK wire from the diode to Splice Pack 100, which is attached to G102 ground point.

See the ELECTRICAL STICKY at the top of this forum for more info on grounds and splice packs.

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Old Aug 19, 2007 | 09:23 PM
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Originally Posted by BlackZ06
Why would you want to force it .... the PCM (it controls the compressor clutch) is programmed to "protect" the compressor if the refrigerant pressure is too low or too high (OK range between 30 psi and 410 psi). The refrigerant has a lubricating oil that lubricates the compressor. If you have no refrigerant then you have no oil.
Can you give us some more info?
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Old Aug 19, 2007 | 10:42 PM
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Old Aug 20, 2007 | 10:15 AM
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Generally you can jumper the low pressure switch with a wire or paper clip. Do not do this for long.
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Old Aug 20, 2007 | 07:47 PM
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Well..a few weeks ago I had to recharge my system. Slow leak (years slow). There was enough pressure in the system to start the AC compressor. However in case this happens again and there is not enough pressure, the AC will not start (actually seems fine now), and then you need to manually start the pump to suck in R134. If the pump is not running, wont be able to fill the system. So basically my question was to prepair for if I needed to do that.
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Old Aug 20, 2007 | 10:34 PM
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As soon as you open the valves on the R134 bottle the pressure will go up high enough for it to start on its on.


Don't force it , I would at least buy a can of 2oz of PAG to add also. If you're leaking gas you are also leaking oil.




Originally Posted by waterzap
Well..a few weeks ago I had to recharge my system. Slow leak (years slow). There was enough pressure in the system to start the AC compressor. However in case this happens again and there is not enough pressure, the AC will not start (actually seems fine now), and then you need to manually start the pump to suck in R134. If the pump is not running, wont be able to fill the system. So basically my question was to prepair for if I needed to do that.
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Old Aug 21, 2007 | 12:19 AM
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I had the same problem. After opening valve on just a 12 oz. can, I waited several minutes and finally the compressor kicked on. It seemed like it took a long time to empty a 12oz can of refrigerant. I then added a 2oz can of lubricant and then another 12oz can of refrigerant. A/C has been working good for weeks.

Good Luck
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Old Aug 21, 2007 | 07:43 PM
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Very good..now I know I wont have a problem.
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