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| [GMCnet] Air conditioning [message #47477] |
Thu, 25 June 2009 05:46  |
Steven Ferguson
Messages: 3447
Registered: May 2006
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For our AC gurus. My
My dash AC shut down. The compressor runs initially but then the
pressure on the low side rises and the pressure switch shuts the
system down. The only way I can measure pressure is on the low side
and it is rising to around 100 psi. I'm suspecting the expansion valve
may be the culprit but am not sure. I'm in OK right now and this is
happening (as usual) at the most inopportune time. It is freaking hot
here!
--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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| Re: [GMCnet] Air conditioning [message #47505 is a reply to message #47498] |
Thu, 25 June 2009 09:54  |
pzerkel
Messages: 212
Registered: September 2007
Location: Salisbury, IL
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This is probably a stupid question. My dash air does not work either. I would like to fix it eventually, but for now the Onan is running and the original roof air can keep it "just barely tolerable". So for now fixing the dash air is somewhere down the list of "stuff I need to fix first".
I want to replace belts, and my stupid question is , "is there any reason to not just remove the a/c compressor belt altogether until I do get around to trouble shooting the dash air?"
If it matters mine is a 78 which I guess has the "better???" air flow.
Thanks,
Paul Zerkel
'78 Eleganza II
Salisbury IL (near Springfield)
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| Re: [GMCnet] Air conditioning [message #47512 is a reply to message #47508] |
Thu, 25 June 2009 10:36 |
GMCWiperMan
Messages: 1248
Registered: December 2007
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George,
I'm not up for a full primer right now, but you problem may be as simple as
a low Freon charge. There's a low pressure cutoff switch on one of the
coolant lines at the right end of the condenser under the hood. That opens,
causing the compressor clutch to disengage, when the coolant gets too low to
circulate lubricant to the compressor. To charge the system, you have to
place a jumper across the contacts in the wire to that switch to allow the
compressor clutch to engage.
As cheap as Duracool (HC-12A) is, a test charge would be my first trouble
shooting step. If the system then cools, you're home free. Unless the
HCZ-12A leaks out. If it does, charge it back up and try to find the leak
with bubble soap. If it doesn't cool, then things get considerably more
complicated.
With your new-found proficiency at Quad Bag installation, you'll be welcome
in Macon when Alan and I install the set he won at Dothan (THANKS, Jim K.).
We'll wait 'til at least August to start (should be real nice & warm by
then).
HTH,
Ken Henderson
Americus, GA
GMCWipersEtc.com
'76 X-Birchaven
-----Original Message-----
To pile onto Paul's email my dash air does not work either. 78 EL II.
The belt is off, but when it was on, the compressor did not engage. Is
there a step by step primer on how to revive/replace the dash AC system?
Advice?
...
George Zhookoff
78 EL II
Snellville, GA
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| Re: [GMCnet] Air conditioning [message #47514 is a reply to message #47512] |
Thu, 25 June 2009 10:53 |
George Zhookoff
Messages: 398
Registered: December 2004
Location: Snellville, GA
Karma: 6
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Ken,
Thanks for the advice. I have several cans of Duracool and a gauge set
w/ vac pump from HF. Let me know when you're doing the Quad bag install
if I can get away I'll be there!
George Zhookoff
78 EL II
Snellville, GA
-----Original Message-----
I'm not up for a full primer right now, but you problem may be as simple
as a low Freon charge. There's a low pressure cutoff switch on one of
the coolant lines at the right end of the condenser under the hood.
That opens, causing the compressor clutch to disengage, when the coolant
gets too low to circulate lubricant to the compressor. To charge the
system, you have to place a jumper across the contacts in the wire to
that switch to allow the compressor clutch to engage.
As cheap as Duracool (HC-12A) is, a test charge would be my first
trouble shooting step. If the system then cools, you're home free.
Unless the HCZ-12A leaks out. If it does, charge it back up and try to
find the leak with bubble soap. If it doesn't cool, then things get
considerably more complicated.
With your new-found proficiency at Quad Bag installation, you'll be
welcome in Macon when Alan and I install the set he won at Dothan
(THANKS, Jim K.).
We'll wait 'til at least August to start (should be real nice & warm by
then).
HTH,
Ken Henderson
Americus, GA
GMCWipersEtc.com
'76 X-Birchaven
-----Original Message-----
To pile onto Paul's email my dash air does not work either. 78 EL II.
The belt is off, but when it was on, the compressor did not engage. Is
there a step by step primer on how to revive/replace the dash AC system?
Advice?
...
George Zhookoff
78 EL II
Snellville, GA
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| Re: [GMCnet] Air conditioning [message #47515 is a reply to message #47477] |
Thu, 25 June 2009 10:58 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
Karma: 0
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| Steven Ferguson wrote on Thu, 25 June 2009 03:46 |
For our AC gurus. My
My dash AC shut down. The compressor runs initially but then the
pressure on the low side rises and the pressure switch shuts the
system down. The only way I can measure pressure is on the low side
and it is rising to around 100 psi. I'm suspecting the expansion valve
may be the culprit but am not sure. I'm in OK right now and this is
happening (as usual) at the most inopportune time. It is freaking hot
here!
--
Steve Ferguson
'76 EII
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Steve and others: your best guess of an expansion valve clog, or even a receiver/dryer issue is probably true. As you know the '76 did not have the best AC to begin with from the flow standpoint, and as Jim B says, a second evaporator would not be a bad idea. But to get you going, the expansion valve is not too expensive until you decide what to do for the long term.
Steve, I have a spare second evaporator of the type Jim suggests, that I would be glad to send you free, let me know if you have any interest.
George: what ken H says is probably the issue, at least to start. Evacuate the system, see if it holds a vacuum, then recharge. The pressure will come up automatically and the low pressure switch will turn the compressor on. If you simply want to see if the compressor runs, without doing any charge, what Ken suggests is fine for a few minutes. Don't run it long that way without a charge.
pzerkle: no real reason to even remove the belt for the AC system until you get around to looking at it. If you don't turn it on (and probably even if you do) the clutch will not engage and try to run the compressor. It will just spin the belt around happily forever until the bearing in the clutch goes out, which is a very long time.
Rob Allen
former owner of '76 x-PB
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| Re: [GMCnet] Air conditioning [message #47516 is a reply to message #47477] |
Thu, 25 June 2009 11:02 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Steve
I doubt if it is the expansion valve as a bad expansion usually means it doesn't feed ( low suction). One hundred pounds is kind of high I'll bet the discharge is really high. If you are checking it in your driveway @ 1500 rpm and high outside temperatures you will likely need to spray a little water on the condenser or it will over heat the system due to no air going thru the condenser. This should lower the suction to around 20-25
lbs (duracool)if the interior isn't too hot. If it is much higher then that you may be overcharged. I assume your switch is the type that opens on a low charge as well as an over pressure condition as it is in the liquid line? Did you check it while driving down the road?
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Air conditioning [message #47519 is a reply to message #47516] |
Thu, 25 June 2009 11:15 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
Karma: 0
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| roy1 wrote on Thu, 25 June 2009 09:02 |
Steve
I doubt if it is the expansion valve as a bad expansion usually means it doesn't feed ( low suction). One hundred pounds is kind of high I'll bet the discharge is really high. If you are checking it in your driveway @ 1500 rpm and high outside temperatures you will likely need to spray a little water on the condenser or it will over heat the system due to no air going thru the condenser. This should lower the suction to around 20-25
lbs (duracool)if the interior isn't too hot. If it is much higher then that you may be overcharged. I assume your switch is the type that opens on a low charge as well as an over pressure condition as it is in the liquid line? Did you check it while driving down the road?
Roy
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Steve: re thinking this in light of Roy's comments makes me agree with him. A plugged expansion valve would result in a low, not a high suction pressure as the compressor is trying hard to pull gas through the system. I hate to say it, but there could be a possibility of internal compressor failure somehow causing high pressure on the suction side. If you find, using Roy's suggestions, you cannot get the pressure down maybe... Hmmmm, interesting problem.
Rob Allen
former owner of '76 x-PB
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| Re: [GMCnet] Air conditioning [message #47524 is a reply to message #47477] |
Thu, 25 June 2009 12:32 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| Steven Ferguson wrote on Thu, 25 June 2009 06:46 |
For our AC gurus. My
My dash AC shut down. The compressor runs initially but then the pressure on the low side rises and the pressure switch shuts the system down.
|
Huh? - I think you have something backwards here.
The pressure switch that is in the line from the evaporator CLOSES ON RISE. Put a jumper in that switch and see if the compressor stays engaged.
| Steve continued |
The only way I can measure pressure is on the low side and it is rising to around 100 psi. I'm suspecting the expansion valve may be the culprit but am not sure.
|
The expansion has two competing functions, it closes when the evaporator pressure is too high and biases toward open as the evaporator outlet temperature rises. The tex does not have a failure mode that would explain this.
| Quote: |
I'm in OK right now and this is happening (as usual) at the most inopportune time. It is freaking hot here!
--
Steve Ferguson
|
I don’t have any documentation with me right now, but if this system has a high side pressure switch, that could be disengaging the compressor. There are two kinds (a non-GMC answer) both a high pressure cutout and a low pressure cutout.
If it is a high pressure cutout, there are two easy reasons: A - There is inadequate airflow through the condenser. Or, B - The system is massively over charged so the condenser is full.
If it is a low pressure cutout, then the system is charge short and not being allowed to run to prevent air and moisture from entering the system and doing more damage.
Go look some more for a high side pressure tap.
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
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| Re: [GMCnet] Air conditioning [message #47537 is a reply to message #47519] |
Thu, 25 June 2009 13:35 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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rob
True but I'm thinking he has a high pressure cutout switch that is shutting it off. If the discharge is excessive it will cause the suction to rise also . A good reason to have a discharge side gage fitting. If this is what is happening it is likely overcharged or not enough air is passing thru the condenser. This is a very possible reason if checking the ac on a hot day in the desert with the engine at 1500 rpm. If the valves are bad in the compressor it probably won't run a real high head pressure.
If the system has non condensibles in it(air) from not being evacuated properly it will have the same symptoms. If it is over charged ditto. On a hot day I always squirt the condenser with water as needed to check the ac when I am checking it at a high idle. If the idle is low (600 rpm)the compressor won't be pumping a whole bunch.
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Air conditioning [message #47546 is a reply to message #47537] |
Thu, 25 June 2009 16:23 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
Karma: 0
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| roy1 wrote on Thu, 25 June 2009 11:35 |
rob
True but I'm thinking he has a high pressure cutout switch that is shutting it off. If the discharge is excessive it will cause the suction to rise also . A good reason to have a discharge side gage fitting. If this is what is happening it is likely overcharged or not enough air is passing thru the condenser. This is a very possible reason if checking the ac on a hot day in the desert with the engine at 1500 rpm. If the valves are bad in the compressor it probably won't run a real high head pressure.
If the system has non condensibles in it(air) from not being evacuated properly it will have the same symptoms. If it is over charged ditto. On a hot day I always squirt the condenser with water as needed to check the ac when I am checking it at a high idle. If the idle is low (600 rpm)the compressor won't be pumping a whole bunch.
Roy
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As I recall, and I sold my coach and all the literature and manuals last week, so I cannot check, the 76 had a low pressure cutout only. If the pressure was too low from lack of any charge it shut the compressor down. Now maybe it was a combined switch which also shut down on too high head pressure, I just don't know if that is true or not. We will have to wait to see if your water misting technique tells any more.
Rob Allen
former owner of '76 x-PB
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| Re: [GMCnet] Air conditioning [message #47548 is a reply to message #47546] |
Thu, 25 June 2009 16:57 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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On Jun 25, 2009, at 3:23 PM, Rob Allen wrote:
>
>
> roy1 wrote on Thu, 25 June 2009 11:35
>> rob
>>
>> True but I'm thinking he has a high pressure cutout switch that is
>> shutting it off. If the discharge is excessive it will cause the
>> suction to rise also . A good reason to have a discharge side gage
>> fitting. If this is what is happening it is likely overcharged or
>> not enough air is passing thru the condenser. This is a very
>> possible reason if checking the ac on a hot day in the desert with
>> the engine at 1500 rpm. If the valves are bad in the compressor it
>> probably won't run a real high head pressure.
>> If the system has non condensibles in it(air) from not being
>> evacuated properly it will have the same symptoms. If it is over
>> charged ditto. On a hot day I always squirt the condenser with
>> water as needed to check the ac when I am checking it at a high
>> idle. If the idle is low (600 rpm)the compressor won't be pumping a
>> whole bunch.
>> Roy
>
>
> As I recall, and I sold my coach and all the literature and manuals
> last week, so I cannot check, the 76 had a low pressure cutout
> only. If the pressure was too low from lack of any charge it shut
> the compressor down. Now maybe it was a combined switch which also
> shut down on too high head pressure, I just don't know if that is
> true or not. We will have to wait to see if your water misting
> technique tells any more.
>
> --
> Rob Allen
> '76 x-PB
There were no high pressure shut off switches on the GMCs. The low
pressure cutoff was not a combined switch either.
Emery Stora
77 Kingsley
Santa Fe, NM
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| Re: [GMCnet] Air conditioning [message #47557 is a reply to message #47524] |
Thu, 25 June 2009 17:42 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Senior Member |
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I checked the manual (X-7525), because I couldn't remember whether the
switch has a high pressure shut off. No, there's no reference to that
function. But the switch does have another function I'd forgotten: Ambient
temperature affects the switching pressure. No table showing what that
correlation is though. This is all I can find: The Compressor Discharge
Pressure Switch should open at 25*F or 37 psi and close at 45*F or 42 psi.
There is a mention that the pressure can momentarily reach 480 psi, but
nothing about what prevents it going even higher.
Ken Henderson
Americus, GA
GMCWipersEtc.com
'76 X-Birchaven
-----Original Message-----
...
I don’t have any documentation with me right now, but if this system
has a high side pressure switch, that could be disengaging the compressor.
There are two kinds (a non-GMC answer) both a high pressure cutout and a low
pressure cutout.
If it is a high pressure cutout, there are two easy reasons: A - There is
inadequate airflow through the condenser. Or, B - The system is massively
over charged so the condenser is full.
If it is a low pressure cutout, then the system is charge short and not
being allowed to run to prevent air and moisture from entering the system
and doing more damage.
Go look some more for a high side pressure tap.
Matt
--
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| Re: [GMCnet] Air conditioning [message #47586 is a reply to message #47505] |
Thu, 25 June 2009 21:39 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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After investigating these add on a/c units we signed up as the Vintage Air
Distributor.It is amazing how little space they use and light as a feather
but cools so well it needs to be turned down. Cost for the unit is around
$500.
Should have a picture on our web site under accessory
We can drop ship to anyone in the US or overseas.
On Thu, Jun 25, 2009 at 7:54 AM, Paul Zerkel <gmc@zerkelhome.com> wrote:
>
>
> This is probably a stupid question. My dash air does not work either. I
> would like to fix it eventually, but for now the Onan is running and the
> original roof air can keep it "just barely tolerable". So for now fixing the
> dash air is somewhere down the list of "stuff I need to fix first".
>
> I want to replace belts, and my stupid question is , "is there any reason
> to not just remove the a/c compressor belt altogether until I do get around
> to trouble shooting the dash air?"
>
> If it matters mine is a 78 which I guess has the "better???" air flow.
>
> Thanks,
> --
> Paul Zerkel
> '78 Eleganza II
> Salisbury IL (near Springfield)
> _______________________________________________
> GMCnet mailing list
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--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Air conditioning [message #47587 is a reply to message #47546] |
Thu, 25 June 2009 22:04 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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Rob
Looks like it was Steve's SOB so that explains why it might have a hi pressure cutout. Otherwise it doesn't make sense that it would cut out on the loss of charge switch with 100 lbs suction and the compressor running.
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Air conditioning [message #47592 is a reply to message #47586] |
Thu, 25 June 2009 22:32 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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| jimk wrote on Thu, 25 June 2009 21:39 |
After investigating these add on a/c units we signed up as the Vintage Air
Distributor.It is amazing how little space they use and light as a feather
but cools so well it needs to be turned down. Cost for the unit is around
$500.
Should have a picture on our web site under accessory
We can drop ship to anyone in the US or overseas.
Jim Kanomata
Applied/GMC, Fremont,CA
|
Nope - I did not find it under "accessory" or "interior". It may be there but I could not find it.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: [GMCnet] Air conditioning [message #47635 is a reply to message #47596] |
Fri, 26 June 2009 14:20 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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George,My people told me that it was going to be done that day.
Love it when they do not tell you what's happening.
On Thu, Jun 25, 2009 at 9:01 PM, George Rudawsky <GeorgeRud@aol.com> wrote:
>
>
> Jim, it's listed under the Accessories heading, but there is no picture
> that shows up.
> --
> George Rudawsky
> Chicago, IL
> 75 Palm Beach
> _______________________________________________
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--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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