AC Compressor Replacment - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Russell · 05-25-2005, 03:38 PM

Hey guys!

The air compressor in my 89 has a broken high pressure switch. I've got a spare 89 compressor that I don't really need, and I was wondering if I would wind up having to get the AC re-charged if I went to change compressors. I would assume that'd be the case, but I wanted to ask just incase there is some sort of a cut off valve that'd prevent the AC system from discharging when you went to change the compressor.

Other question, just how crucial IS the high pressure switch? Can I run the AC without it, or am I beggin to blow something up? For example, can I just put a timer on in place of the sensor, so it runs the AC compressor for maybe 20 - 30 seconds, then shuts off or something?

The compressor that is on there is good, its just the switch end that is broken off.

NeCrOmAnCeR · 05-25-2005, 11:01 PM

Changing compressors requires the system to be evacuated. To use some sort of timer you would have to know the exact cooling load, ambient temp, airflow through the condensor etc... All these things change while driving (vehicle stoped, moving down the highway etc...) this is why the pressure switch is necessary, to be sure that the refrigerant pressure doesn't become excessive when the vehicle motion is stopped (high-side pressure goes up). Replace the switch!!

Russell · 05-26-2005, 12:03 AM

alright, I'll just leave it be with the compressor disconnected then. I don't wanna bother with the hassle of getting it recharged later.

VetNutJim · 05-26-2005, 01:49 AM

If you choose to swap compressors you will need to have the system evacuated and recharged.

Same with replacing the pressure switch on the exisitng compressor.....but a LOT less work and much less chance of contaminating the sealed system.

As stated above: Change the switch

454HO · 05-26-2005, 02:44 PM

Is this an R12 system or an R134a conversion? The high side switch is important either way, but it's critical if you are running R134a.

If by chance you have a schrader valve port on the high pressure line, you might can get an aftermarket pressure switch and attach it to that port without losing your freon charge.

Russell · 05-26-2005, 03:21 PM

thats something to look into 454HO

I never use the AC system, but I am planning on getting rid of the truck right away, so I thought that I might just fix it and call it good. But if it means I gotta pay to get the system recharged, I just won't bother and leave the compressor solenoid dissconnected

05-25-2005, 03:38 PM	#1
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	AC Compressor Replacment Hey guys! The air compressor in my 89 has a broken high pressure switch. I've got a spare 89 compressor that I don't really need, and I was wondering if I would wind up having to get the AC re-charged if I went to change compressors. I would assume that'd be the case, but I wanted to ask just incase there is some sort of a cut off valve that'd prevent the AC system from discharging when you went to change the compressor. Other question, just how crucial IS the high pressure switch? Can I run the AC without it, or am I beggin to blow something up? For example, can I just put a timer on in place of the sensor, so it runs the AC compressor for maybe 20 - 30 seconds, then shuts off or something? The compressor that is on there is good, its just the switch end that is broken off. __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap) Last edited by Russell; 05-25-2005 at 03:39 PM.

05-26-2005, 12:03 AM	#3
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	alright, I'll just leave it be with the compressor disconnected then. I don't wanna bother with the hassle of getting it recharged later. __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

05-26-2005, 02:44 PM	#5
454HO Registered User Join Date: Apr 2005 Location: Austin, TX Posts: 1,223	Is this an R12 system or an R134a conversion? The high side switch is important either way, but it's critical if you are running R134a. If by chance you have a schrader valve port on the high pressure line, you might can get an aftermarket pressure switch and attach it to that port without losing your freon charge. __________________ - Greg

05-26-2005, 03:21 PM	#6
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	thats something to look into 454HO I never use the AC system, but I am planning on getting rid of the truck right away, so I thought that I might just fix it and call it good. But if it means I gotta pay to get the system recharged, I just won't bother and leave the compressor solenoid dissconnected __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

05-25-2005, 11:01 PM	#2
NeCrOmAnCeR Registered User Join Date: Feb 2004 Location: Hodgenville, Ky Posts: 735	Changing compressors requires the system to be evacuated. To use some sort of timer you would have to know the exact cooling load, ambient temp, airflow through the condensor etc... All these things change while driving (vehicle stoped, moving down the highway etc...) this is why the pressure switch is necessary, to be sure that the refrigerant pressure doesn't become excessive when the vehicle motion is stopped (high-side pressure goes up). Replace the switch!!

05-26-2005, 01:49 AM	#4
VetNutJim Registered User Join Date: Apr 2004 Posts: 9	If you choose to swap compressors you will need to have the system evacuated and recharged. Same with replacing the pressure switch on the exisitng compressor.....but a LOT less work and much less chance of contaminating the sealed system. As stated above: Change the switch



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