| A/C compressor [message #128295] |
Thu, 02 June 2011 09:06  |
thorndike
Messages: 406
Registered: January 2011
Location: Conifer, Colorado
Karma: 0
|
Senior Member |
|
|
Good afternoon,
In my efforts to get my GMC ready to go, I noticed that when I turn on the dash air, I have no indication that the A/C compressor is starting up. There is no momentary drop in engine RPMs, no compressor sound, etc. Obviously I have a problem.
Before I start randomly trying to solve this, are there any suggestions as to the likely cause that I should check first?
Bob
Robert Peesel
1976 Royale 26'
Side Dry Bath
Conifer, Colorado
|
|
|
|
| Re: A/C compressor [message #128319 is a reply to message #128295] |
Thu, 02 June 2011 11:26  |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
|
Senior Member |
|
|
| thorndike wrote on Thu, 02 June 2011 10:06 |
Good afternoon,
In my efforts to get my GMC ready to go, I noticed that when I turn on the dash air, I have no indication that the A/C compressor is starting up. There is no momentary drop in engine RPMs, no compressor sound, etc. Obviously I have a problem.
Before I start randomly trying to solve this, are there any suggestions as to the likely cause that I should check first?
Bob
|
Bob,
Out in the front is a switch in the suction line. This is a low pressure cut-off switch, and if the charge has leaked down too much the compressor won't even start. First thing to do is jump that that switch, if the compressor starts don't let it run long.
That means the system is charge short. It may have a leak that actually needs fixing, but get something in it first.
Matt
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
|
|
|
|
| Re: A/C compressor [message #128390 is a reply to message #128295] |
Thu, 02 June 2011 18:54 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
|
Senior Member |
|
|
Matt is totally correct in his advice. But, you may be lucky as ALL automotive AC systems leak, by design, and they all leak at different rates. If your system was low last fall, enough charge may have leaked out over winter, compounded by disuse and lack of oil distribution, to get just below the trigger point on the switch. You may need 1.5 cans or more to be back to full charge. If you are losing less than a pound a year, in my mind I would just top off each year, or maybe run the unit more assuming moderate temps later into the fall and sooner in the spring so it doesn't sit so long idle. This seems to help at the compressor seal, but won't do much if the swag joints are failing on the hoses. With leaks you have to decide when it is worth the effort to discharge and repair. I'm assuming R12. Once charged you can have the system checked with one of the sniffer tools to try to see where the leak(s)is/are. But if your system has not been charged in several years, the leak rate may still be very low and you werer just due for a recharge. Good luck.
John Lebetski
Woodstock, IL
77 Eleganza II
|
|
|
|
| Re: A/C compressor [message #128397 is a reply to message #128295] |
Thu, 02 June 2011 20:29 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
|
Senior Member |
|
|
| thorndike wrote on Thu, 02 June 2011 08:06 |
Good afternoon,
In my efforts to get my GMC ready to go, I noticed that when I turn on the dash air, I have no indication that the A/C compressor is starting up. There is no momentary drop in engine RPMs, no compressor sound, etc. Obviously I have a problem.
Before I start randomly trying to solve this, are there any suggestions as to the likely cause that I should check first?
Bob
|
Does your blower fan come on? Also there is a switch mounted to the evaporator which will control icing if the temp gets too cold. There is a wire that is in series with the low pressure switch that leads to the switvh hidden behind the evaporator cover--make sure it is plugged in or jumper across the connector to check if the switch is open. And then of course, double check the connector at the compressor clutch.
Bob de Kruyff
78 Eleganza
Chandler, AZ
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
