| [GMCnet] AC Question [message #287253] |
Mon, 14 September 2015 12:50  |
Gary Berry
Messages: 1002
Registered: May 2005
Karma: -1
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Senior Member |
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Hey;
I charged my AC system yesterday and according to the gauge I'm getting
35lbs on the low side while running. When I shut the engine off, the low
side goes to 70lbs. I let it set there overnight and when I looked at the
low side gauge this morning, it's sitting at 15lbs. Is this normal or
should it be higher than that when not being used?
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Gary and Diana Berry
73 CL Stretch in Wa.
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| Re: [GMCnet] AC Question [message #287256 is a reply to message #287253] |
Mon, 14 September 2015 13:14  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Gary,
The simple fact is that a refrigeration system, when shut down, should have liquid in it someplace. That liquid will express a vapor pressure for that temperature. Ergo, if it isn't below freezing where you are, I would suspect you have a leak.
Matt
Gary Berry wrote on Mon, 14 September 2015 13:50Hey;
I charged my AC system yesterday and according to the gauge I'm getting 35lbs on the low side while running. When I shut the engine off, the low side goes to 70lbs. I let it set there overnight and when I looked at the low side gauge this morning, it's sitting at 15lbs. Is this normal or should it be higher than that when not being used?
--
Gary and Diana Berry
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] AC Question [message #287263 is a reply to message #287253] |
Mon, 14 September 2015 14:23 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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2 discussions going on here. Runing and static. Lots of temp and speed variables running. Off it is what the VP is at that ambient. See Duracool chart. At shut down you have hot condenser and non equalized pressures, that after a few mins should be equal throughout the System, though temporarily skewed.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] AC Question [message #287285 is a reply to message #287253] |
Mon, 14 September 2015 18:39 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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To put it another way, the low side pressure should drop and hi side go up from the static VP state when the comp starts running.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] AC Question [message #287378 is a reply to message #287300] |
Wed, 16 September 2015 11:34 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Bullitthead wrote on Mon, 14 September 2015 23:27Stop leak in A/C system= end of system functionality...just from others' experience, YMMV 
I've used stop leak in several systems including my GMC and they all continued to work just fine.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] AC Question [message #287380 is a reply to message #287253] |
Wed, 16 September 2015 12:00 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Stop leak might be ok for very small losses. He had full system leakdown. .
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] AC Question [message #287431 is a reply to message #287380] |
Thu, 17 September 2015 00:39 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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I've just had 3 customers that had functioning systems that leaked (evaporator, condenser, and compressor manifold) and they each tried the product that had a sealer of some kind in it. First one fortunately just lost a belt (and came in on the hook) because the orifice tube sealed up and stopped the flow in the system. Second one had an auxiliary system in a van and the sealer locked the expansion valve on it while the main system continued to function normally. The last one had to replace the compressor that stopped making pressure 2 days after installing the refrigerant with the sealer included.
Doing the repairs on those vehicles for them made me decide to not install it in any of my systems. I'm sure it has worked on many systems out there, so YMMV . Like John said, it's not going to seal a leak that vents the system overnight, and it most likely will not seal a leaking shaft seal after the shaft rotates. (Unless the leak is around the outside of the seal)
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
[Updated on: Fri, 18 September 2015 21:07] Report message to a moderator |
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| Re: [GMCnet] AC Question [message #287445 is a reply to message #287443] |
Thu, 17 September 2015 14:46 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Gary,
If you can't find a UV light with you love beads and bell bottoms, go on E-bays and buy a UV flashlight for less than 10$us, then go over to Hazard Fright and buy a pair of yellow glasses to go with that. then trace dye works great.
Note: If it is the shaft seal leaking, the trace dye may be all over, but it will be surrounding the shaft.
Matt - heading into Pueblo
Gary Berry wrote on Thu, 17 September 2015 14:36Hey All;
So I'm reluctant to throw an stop leak at it (but i will if I need to).
I decided to replace the 4 seals for the dryer/accumulator. One of them on the low side was pretty tore up but I couldn't tell if it happened when I put the system together or when I pulled the hose out. Anyway, I've pumped the system down again to 25 inches of vacuum and when I stop the pump and close all of the valves, the system dropped to 15 inches of vacuum in a couple of hours. I left it for a couple of days and it pretty much sat at 10 inches for 2 nights. I decided to pump it down again (25 inches) and now it's dropped to 15 inches of vacuum and is holding pretty steady. I'll check it tonight and see where it's at. I'm thinking about throwing a couple of more cans of Duracool at it to pressurize the system. Is there anything I can put into the system that might show me where the leak is? I don't currently have a black light, but I can probably dig into my 70's
trunk and pull one out...
--
Gary and Diana Berry
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] AC Question [message #287447 is a reply to message #287253] |
Thu, 17 September 2015 16:09 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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Gary, I do not like the sealer, this is not recomended but how I do it... I have 3air dryers I can put in my shop air, I have an adapter to shop air my gauges. I put 120 lb on the system and shut off the valves. Get out the soapy water spray. Check your Gage's and lines first. Drawback is it ends up cleaner.soak ever stuff, connections, lines, in a few minutes it should show. Check in front of radiator for rock damage. I did have one that would not hold vacuum till I put shop air on it and could find no bubbles anywhere, but it held 120 overnight. I bled it off put a 3 hr vacuum on it held -22 overnight. Only thing I figure is the pressure seated the seal?
C. Boyd
76 Crestmont
East Tennessee
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| Re: [GMCnet] AC Question [message #287468 is a reply to message #287454] |
Thu, 17 September 2015 21:00 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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That's right Chuck, the pressure seated that ceramic seal...had that happen a couple of times. Sometimes they won't hold the full vacuum when they are new. Gary, as a test, try drawing the full vacuum, stopping and blocking off the vac line, and turn the compressor by hand and watch the gauge to see if any vacuum gets released while you turn it slowly. And don't forget about the residual refrigerant that will boil out of the lubricant in the system. That takes time and can screw up your overnight observations.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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