Home » Public Forums » GMCnet » '78 Dash A/C
| '78 Dash A/C [message #170437] |
Mon, 21 May 2012 15:30  |
 |
JShot
Messages: 485
Registered: October 2006
Location: NW Ohio
Karma: 0
|
Senior Member |
|
|
Went out camping for the weekend, and tried the dash A/C on the way home today. It still works from last year when we changed over to Duracool! Amazing! But the compressor runs (howls) for 20 seconds and the air gets REAL cold, then the compressor shuts off for 20 seconds, and the air gets outside hot. 20 on, 20 off. That seems like too much cycling. Do I need to check the refrigerant "level" again? Does it sound low? If it's low, and I add some more Duracool, will the dash air still get as cold?
Thanks,
John
John Shotwell
Ridgeville Corners, OH
78 Royale Center Kitchen
|
|
|
|
| Re: '78 Dash A/C [message #170442 is a reply to message #170437] |
Mon, 21 May 2012 16:44  |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
|
Senior Member |
|
|
| JShot wrote on Mon, 21 May 2012 14:30 |
Went out camping for the weekend, and tried the dash A/C on the way home today. It still works from last year when we changed over to Duracool! Amazing! But the compressor runs (howls) for 20 seconds and the air gets REAL cold, then the compressor shuts off for 20 seconds, and the air gets outside hot. 20 on, 20 off. That seems like too much cycling. Do I need to check the refrigerant "level" again? Does it sound low? If it's low, and I add some more Duracool, will the dash air still get as cold?
Thanks,
John
|
There's a cycling switch in front of the evaporator. It may be mispositioned. I can't explain the howling compressor however. I would definitely check the refrigerant first.
Bob de Kruyff
78 Eleganza
Chandler, AZ
|
|
|
|
| Re: [GMCnet] '78 Dash A/C [message #170444 is a reply to message #170437] |
Mon, 21 May 2012 17:24 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
|
Senior Member |
|
|
Could it be the belt making the noise?
FREE WIFI @ Mickey D
On May 21, 2012, at 1:30 PM, John Shotwell <jshot@rtecexpress.net> wrote:
>
>
> Went out camping for the weekend, and tried the dash A/C on the way home today. It still works from last year when we changed over to Duracool! Amazing! But the compressor runs (howls) for 20 seconds and the air gets REAL cold, then the compressor shuts off for 20 seconds, and the air gets outside hot. 20 on, 20 off. That seems like too much cycling. Do I need to check the refrigerant "level" again? Does it sound low? If it's low, and I add some more Duracool, will the dash air still get as cold?
>
> Thanks,
>
> John
> --
> John Shotwell
> Ridgeville Corners, OH
> 78 Royale Center Kitchen
> Web Site: GMCmhRegistry.com /
> Email: john@gmcmhregistry.com
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: '78 Dash A/C [message #170445 is a reply to message #170437] |
Mon, 21 May 2012 17:40 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
|
Senior Member |
|
|
Hi Shot: When I first redid my ac system I put 134a in and it worked good, then leaked out some over the winter and would not start the compressor so I evacuated then recharged with 3 cans 12a. It worked all summer and over the winter it leaked just enough to cycle as yours is doing so I added another can and has worked 2 seasons now with no additions. Just what happened to me..
| JShot wrote on Mon, 21 May 2012 16:30 |
Went out camping for the weekend, and tried the dash A/C on the way home today. It still works from last year when we changed over to Duracool! Amazing! But the compressor runs (howls) for 20 seconds and the air gets REAL cold, then the compressor shuts off for 20 seconds, and the air gets outside hot. 20 on, 20 off. That seems like too much cycling. Do I need to check the refrigerant "level" again? Does it sound low? If it's low, and I add some more Duracool, will the dash air still get as cold?
Thanks,
John
|
C. Boyd
76 Crestmont
East Tennessee
|
|
|
|
| Re: '78 Dash A/C [message #170471 is a reply to message #170437] |
Mon, 21 May 2012 21:09 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
| JShot wrote on Mon, 21 May 2012 13:30 |
Went out camping for the weekend, and tried the dash A/C on the way home today. It still works from last year when we changed over to Duracool! Amazing! But the compressor runs (howls) for 20 seconds and the air gets REAL cold, then the compressor shuts off for 20 seconds, and the air gets outside hot. 20 on, 20 off. That seems like too much cycling. Do I need to check the refrigerant "level" again? Does it sound low? If it's low, and I add some more Duracool, will the dash air still get as cold?
Thanks,
John
|
As it has been suggested the cold air temperature thermostat may be set too high I believe they are adjustable. If so place the sensing bulb in a glass of cold ice water and set to around 36 degrees cut out. Also you could be a little low on Duracool this will lower the discharge air off the coil and cause the thermostat we talked about to open. Check the suction pressure at 1500 RPM it should be around 25 or pounds if it is much less you are low on refrigerant.
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
|
| Re: '78 Dash A/C [message #170482 is a reply to message #170471] |
Mon, 21 May 2012 23:26 |
John Sharpe
Messages: 489
Registered: February 2006
Location: Texas
Karma: 1
|
Senior Member |
|
|
| Quote: |
..... ac compressor 20 on, 20 off.....
|
I suspect the high side has too low a pressure and you are cycling on the low pressure switch. Probably need a bit more refrigerant (12a). As Bob, Chuck, and roy1 suggested, Low pressure between 20-25 @ 1500.
John Sharpe
Humble,TX
'78 Eleganza TBI
'89 Spectrum 2000 MPI V-10
'40 Ford Panel Delivery TPI
johnasharpe@gmail.com
|
|
|
|
| Re: '78 Dash A/C [message #170523 is a reply to message #170482] |
Tue, 22 May 2012 10:58 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
| John Sharpe wrote on Mon, 21 May 2012 21:26 |
| Quote: |
..... ac compressor 20 on, 20 off.....
|
I suspect the high side has too low a pressure and you are cycling on the low pressure switch. Probably need a bit more refrigerant (12a). As Bob, Chuck, and roy1 suggested, Low pressure between 20-25 @ 1500.
|
Does the 78 have a low pressure switch?? My 76 only has a loss of charge switch in the liquid line. Just wondering.
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
|
|
|
| Re: [GMCnet] '78 Dash A/C [message #170531 is a reply to message #170525] |
Tue, 22 May 2012 12:11 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
[quote title=emerystora wrote on Tue, 22 May 2012 09:12]
On May 22, 2012, at 9:58 AM, roy@gmcnet.org wrote:
>
>
> John Sharpe wrote on Mon, 21 May 2012 21:26
>> Quote:
>>> ..... ac compressor 20 on, 20 off.....
>>
>>
>> I suspect the high side has too low a pressure and you are cycling on the low pressure switch. Probably need a bit more refrigerant (12a). As Bob, Chuck, and roy1 suggested, Low pressure between 20-25 @ 1500.
>
>
>
> Does the 78 have a low pressure switch?? My 76 only has a loss of charge switch in the liquid line. Just wondering.
> --
> Roy Keen
Roy - that is a low pressure switch. If you are getting low on charge it will cause the compressor clutch to cycle on and off. If you lose you charge totally it will not allow the compressor clutch to run at all.
Emery Stora
Yeah but being in the liquid line it only locks the compressor out when you are very low on refrigerant that is why it is called a loss of charge switch.If the system were a little low on refrigerant this type of low pressure control won't cycle the compressor as it is located on the high pressure side, the evap coil thermostat will cycle it. If it were in the suction line it would be a true low pressure switch and the compressor would cycle on and off with just a partial loss of charge. Some of the newer vehicles have both a high pressure cutout in the discharge or liquid line and a low pressure cutout in the suction line. I was just wondering if the 78 actually had a low pressure control in the suction line.
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
|
|
|
|
|
| Re: '78 Dash A/C [message #170573 is a reply to message #170437] |
Tue, 22 May 2012 19:25 |
kingd
Messages: 592
Registered: June 2004
Karma: 2
|
Senior Member |
|
|
Yikes, I try not to be critical of things being done by other people but I notice 2 potentially EXPENSIVE statements in the posts of this thread. The original poster said he had Duracool in his system and someone said top it up with R12, yes I know they are cpmpatible but now you have a mixed system that a LOT of places will NOT evacuate and it is ILLEGAL to vent to the atmosphere. Some one else had R134 in his system and topped it up with R12. These are NOT compatible. I also haven't heard of an oil that works with both. Hope he doesn't end up with a damaged system. Not trying to be picky !!!
DAVE KING
P.S. I did read the thread twice to try to keep foot out of mouth
DAVE KING
lurker, wannabe
Toronto, Ontario, Canada
|
|
|
|
| Re: '78 Dash A/C [message #170575 is a reply to message #170573] |
Tue, 22 May 2012 19:43 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
| kingd wrote on Tue, 22 May 2012 17:25 |
Yikes, I try not to be critical of things being done by other people but I notice 2 potentially EXPENSIVE statements in the posts of this thread. The original poster said he had Duracool in his system and someone said top it up with R12, yes I know they are compatible but now you have a mixed system that a LOT of places will NOT evacuate and it is ILLEGAL to vent to the atmosphere. Some one else had R134 in his system and topped it up with R12. These are NOT compatible. I also haven't heard of an oil that works with both. Hope he doesn't end up with a damaged system. Not trying to be picky !!!
DAVE KING
P.S. I did read the thread twice to try to keep foot out of mouth
|
The oil used with 134 can be used with R12. R12 oil which is mineral oil isn't compatible with 134. You are correct no one will want to recover a Duracool R12 mix but it will work OK in the system. If you top off a 134 system with R12 the system should have PAC or Ester oil in it so it will function OK as the operating pressures are close and they will mix. The only problem is charging with 134 if oil used is Mineral oil. R12 and Duracool are happy with any of the oils.
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
|
|
|
| Re: [GMCnet] '78 Dash A/C [message #170619 is a reply to message #170586] |
Wed, 23 May 2012 10:45 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
[quote title=emerystora wrote on Tue, 22 May 2012 19:19]Yes, but my question is why??? R12 is expensive and getting harder to find -- also it is not as efficient as Duracool.
Emery Stora
On May 22, 2012, at 6:43 PM, roy@gmcnet.org wrote:
>
>
> kingd wrote on Tue, 22 May 2012 17:25
>> Yikes, I try not to be critical of things being done by other people but I notice 2 potentially EXPENSIVE statements in the posts of this thread. The original poster said he had Duracool in his system and someone said top it up with R12, yes I know they are compatible but now you have a mixed system that a LOT of places will NOT evacuate and it is ILLEGAL to vent to the atmosphere. Some one else had R134 in his system and topped it up with R12. These are NOT compatible. I also haven't heard of an oil that works with both. Hope he doesn't end up with a damaged system. Not trying to be picky !!!
>>
>> DAVE KING
>> P.S. I did read the thread twice to try to keep foot out of mouth
>
>
>
> The oil used with 134 can be used with R12. R12 oil which is mineral oil isn't compatible with 134. You are correct no one will want to recover a Duracool R12 mix but it will work OK in the system. If you top off a 134 system with R12 the system should have PAC or Ester oil in it so it will function OK as the operating pressures are close and they will mix. The only problem is charging with 134 if oil used is Mineral oil. R12 and Duracool are happy with any of the oils.
> --
> Roy Keen
> Minden,NV
> 76 X Glenbrook
> _______________________________________________
>Emory I agree 100% if I didn't have any R12 I would use Duracool R12 is too damn expensive I can remember when anyone could buy 30 lbs of R12 for $30 . Duracool is a little more efficent than R12 but I kind of like working with R12 rather then Duracool its easier to weigh in & the sight glass still works. I also would rather have Duracool than 134 as it is noticebly more efficient and colder. You make a good point.
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
|
|
|
| Re: [GMCnet] '78 Dash A/C [message #170631 is a reply to message #170625] |
Wed, 23 May 2012 12:55 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
[quote title=emerystora wrote on Wed, 23 May 2012 09:43]Roy. -- I thought that you said in a former post that you were going to top up a Durocool system with R 12.
If that is the case then your sight glass is not going to work as it will show bubbles even when fully charged.
Emery Stora
>> __________________
>> Emery I agree 100% if I didn't have any R12 I would use Duracool R12 is too damn expensive I can remember when anyone could buy 30 lbs of R12 for $30 . Duracool is a little more efficent than R12 but I kind of like working with R12 rather then Duracool its easier to weigh in & the sight glass still works. I also would rather have Duracool than 134 as it is noticeably more efficient and colder. You make a good point.
> --
> Roy Keen
> Minden,NV
> 76 X Glenbrook
> ___
As you know that would not be legal to do so and then have an air condition shop recover it and send it to a reclaim outfit. My motor home has 100% R12 in it till I run out. I will say that as far as adding a small amount of R12 to top off the Duracool cause you were out of Duracool or you didn't want to waste the major amount left in the can and you had a little R12 laying around it would work but most folks don't have small amounts laying around. I have 4 different types of refrigerant in my garage. I have a recovery machine and some recovery tanks . I always try to recover the charge that may be left, fix a problem and then put it back in. It's not that easy to find Duracool around here the stores don't have it. It needs to be shipped and that takes time when you are already in the process of charging your system. If I were working on a vehicle that was designed for 134 that is what I would use because I have a 30 lb cylinder. I just replaced a compressor in a Friends truck I recovered what 134 was in the system then put it back in & the 2 - 12 ounce cans he gave me which wasn't quite enough so I gave it a few ounces from my 30 lb can.
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
|
Goto Forum:
Current Time: Wed Oct 02 05:20:38 CDT 2024
Total time taken to generate the page: 0.12078 seconds
|
GMCforum
Search
Help
Register
Login
Home
