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2013 Chevrolet Suburban
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AC Clutch not engaging, 140psi showing at Low Pressure tap

Old June 18th, 2019, 12:28 PM
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Default AC Clutch not engaging, 140psi showing at Low Pressure tap

04 Suburban 1500 5.3L

Symptoms:
* AC no longer cool (last used in fall)
* Compressor clutch not engaging
* DIY recharge kit meter shows ~140psi at low press tap
* All 3 AC related fuses are good
* Voltmeter found 13vdc (on 2 of the 4 sockets ) and ground under the AC relay
* Struggling to access electrical plug at clutch so I'm not sure if it is powered

Questions:
* Why 140psi at low pressure tap if compressor is off?
* Is there an easier access point to check if clutch is directly getting pwr?
* Should I suspect pressure cutoff switches?
* Knowing these symptoms, what troubleshooting chronology should I follow?
* If problem is somehow due to low freon, how to recharge with that much pressure?

Sincerely would appreciate any help!!!
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Old June 18th, 2019, 1:22 PM
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Some new information/symptoms:

Started it up this morning and the $#!%&@ ac is now working!

Low pressure tap now reads on the hi side of "normal" range but the tap is slowly leaking out. If I put a finger over it I can feel it pressurize underneath with freon.

Does the tap act also as an over-pressure relief or do I need to replace it because it is leaking?
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Old June 18th, 2019, 1:36 PM
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Originally Posted by Qurph View Post
Some new information/symptoms:


Does the tap act also as an over-pressure relief or do I need to replace it because it is leaking?
it should not leak out of either high or low side service port. if the caps were not in place, dirt may have entered the valve. professionals would recover the system, depress and blow out the valve or replace the core.
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Old June 18th, 2019, 5:05 PM
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They now have a tool that allows the tech to replace a Schrader valve without taking the freon out of the system first. In other words they can replace the Schrader valve with the freon still in the system. While it might be a DIY job, the tool is very expensive.
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Old June 18th, 2019, 6:21 PM
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The 140 PSI pressure with the system off is the standard pressure at ambient temperatures for R134. That's why I store partially used cans of freon in the freezer to lower the pressure so it doesn't leak out. I would expect the same pressure on the high side port.
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Old June 18th, 2019, 9:21 PM
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Thanks all for your responses, feels like I'm taking an AC101 class and am just starting to understand the system.

AC clutch stopped engaging after my first drive this a.m. so I'm back to square one. Wish I knew where to start looking.
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Old June 18th, 2019, 9:57 PM
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Are you getting 12V at the clutch? If not, then check the High and Low pressure cutout switches.
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Old June 19th, 2019, 11:03 AM
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Get a real set of service gauges, not some wish kit with just a low side thingee. I hope the refrigerant you added with that thing in the past did NOT contain any sealers, those can be permanent death to an AC system.


Originally Posted by 73shark View Post
Are you getting 12V at the clutch? If not, then check the High and Low pressure cutout switches.
Above is good advice too. Most AC issues stem from refrigerant leakage, but blindly adding refrigerant or a miracle kit is not a good idea.
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Old June 19th, 2019, 11:12 AM
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Can't remember if the 2004 still had the single clutch fan or dual electric fans. If electric fans, make sure the one behind the condenser is working all the time.

Also make sure the condenser is not clogged up. Both will cause instant high pressure because the coolant can't condense back down to liquid.
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Old June 20th, 2019, 8:29 AM
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Originally Posted by Qurph View Post
AC clutch stopped engaging after my first drive this a.m. so I'm back to square one. Wish I knew where to start looking.
Originally Posted by 73shark View Post
Are you getting 12V at the clutch? If not, then check the High and Low pressure cutout switches.
For the record, just yesterday I worked on my 1998 Frontier AC because I had intermittent AC clutch engagement even though I had 12 volt positive getting to the clutch (I have a light wired in parallel to the clutch wire on this). So I removed the AC clutch drive plate and there were two shim spacers under it, and I removed the thinnest one to decrease the clutch gap. I've only driven 8 miles since then, hoping that handled it.

Was my AC clutch getting hot??? Well, it is Arizona !!!
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