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compressor blues

93z on Sun July 06, 2008 6:04 PM User is offline

Year: 1993
Make: chevy
Model: z28
Engine Size: 5.7
Refrigerant Type: 134a

I need help locating my problem.i have a93 z28 original owner,low miles. about 2 months ago the compressor stated to make a sound like the bearings were going bad.shortly after the compressor starter to run intermittently.i thought it was about time to change the compressor,so i changed the compressor,accumulator,and expansion valve.the system was vacuumed,and i added the same amount of oil i took out.my problem is i cannot get the compressor to engage.i have jumped the relay to see if it was getting power, and the compressor will engage,along with the fans.i have also change the relay,and the high pressure switch with negative results.i have jumped the low pressure switch to see if i could get the clutch to engage once again with negative results.the vehicle is not showing any faulty engine codes.also the old compressor was still in good condition.any help would be appreciated,thanks in advance.


Chick on Sun July 06, 2008 6:11 PM User is offlineView users profile

Did you pull a deep vacuum and allow the vacuum to pull in as much refrigerant as it could before trying to finish charging?

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

GM Tech on Sun July 06, 2008 6:28 PM User is offline

Did you reset your code 46 low refrigerant code- that is not a SES light?-- it takes a scan tool to know that code exists... but you can reset it by disconnecting battery for 10 seconds.. also-- NEVER try to jump a three wire pressure transducer-- it is NOT a switch.. you can fry your ECM if you are not careful

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

93z on Sun July 06, 2008 7:18 PM User is offline

thanks for your fast reply s.i have disconnected the battery to the vehicle for at least 10 minutes at a time.the switch that i jumped was in the low pressure line its only a 2 wire switch.my next step is to go to the library,maybe i can find a schematic that shows what the voltage on the wires/switches should be.

Chick on Sun July 06, 2008 7:30 PM User is offlineView users profile

You didn't answer the vacuum question, so I have to make this clear, you need to pull a deep vacuum, next, the computer send a ground signal to the relay, so as GM tech stated, you might need a scan tool to clear the codes if the battery disconnect didn't do it. Jumping the relay made it work:? then the problem is most likely the relay not getting a signal from the computer...

Also, what is your z28? a car, truck? z28 is a trim level, what model is the car/truck? like C/K cavalier, camaro etc..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

93z on Sun July 06, 2008 7:47 PM User is offline

its a 93 camaro,just so i understand what your saying is that i need to run a deep vacuum(i had vacuum the system for 30 min) how long do you recommend i vacuum the system for? Jumping the relay made the compressor cycle on along with jumping the low pressure switch.thanks in advance.

mk378 on Sun July 06, 2008 8:25 PM User is offline

Do you have any charge in the system? Do not run the compressor in vacuum. Charge as much as you can as liquid with the engine off, that should provide enough pressure to close the switch. Then start the engine and A/C and finish the charge as gas thru the low side.

93z on Sun July 06, 2008 8:35 PM User is offline

the system has no freon in it.i"ve never added freon as liquid before.if you don't mind explaining this to me. thanks

Chick on Sun July 06, 2008 9:08 PM User is offlineView users profile

That would explain why it is not running, you need at least 40psi to close all switches and let the computer know when to send the signal to the relay. Pull a deep vacuum, the 30 minutes is enough, then charge liquid into the high side until the vacuum stops drawing it in, then close the high side valve, and finish charging the factory amount (93 Camaro is r134a right?) thru the low side port. The refrigerant drawn thru the vacuum will let the switches tell the computer the system isn't empty and it should start on it's on until full... Reset the codes before charging and it should go right in..Let us know how it turns out..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

93z on Sun July 06, 2008 9:20 PM User is offline

thanks for that reply.ill try that tomorrow after work,ill let you know if it works.

GM Tech on Mon July 07, 2008 8:18 AM User is offline

FYI-- the 2 prong low pressure switch near shock tower is after the relay in the wiring diagram-- the relay switches 12v to the LPCO switch , then that feeds directly to the compressor- the PCM counts compressor cycles and time between cycles and monitors evap probe temp to determine low charge- to set the code 46-- so unless you have been running it for awhile- the code 46 will not come back yet-- it takes awhile 10 minutes or so to set it...

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

93z on Sun July 13, 2008 6:12 PM User is offline

chick you were right, i charged liquid into the high side,then finished it off on the low side,its working great...thanks.

TRB on Sun July 13, 2008 7:10 PM User is offlineView users profile

Chick rocks! As do all the members which help around here!

Now if we could just get Chick to understand the color of orifice tubes we would be set!

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