| Duracool and AC Compressor Pressure Cut-Off Switch [message #215262] |
Sun, 21 July 2013 19:22  |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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After getting the Sequoia started, the primary objective being to get some air in the bags to raise the rump, I was fiddling with the heater/ac controls while the compressor and the bags did their thing.
No fan at any settings. And no AC compressor action when the dash control is on "A/C".
Looking at the wiring diagram to figure out what to trace, I figured the AC compressor cut-off switch might be keeping the compressor from coming on (probably low of freon). To figure out where it is located, I looked at the MM. And I read what the MM says:| Quote: |
The compressor should not run below 25°F. ambient or 37 psi at the switch. The compressor should run in A/C modes above 45°F. ambient or 42 psi at the switch.
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That leads me to believe the pressure switch is looking for something over 37PSI.
Emery Stora once posted that, at 1500 RPM and 80F, the low pressure side when running Duracool would be about 20PSI.
Does everyone charged with Duracool bypass the low pressure switch or what?
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| Re: Duracool and AC Compressor Pressure Cut-Off Switch [message #215267 is a reply to message #215262] |
Sun, 21 July 2013 20:29  |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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The only reason to bypass it is if you are low on refrigerant and adding more to the system. Once there is enough in the system it doesn't need to be jumped. Actually it is really a loss of charge switch. If you jump it and the compressor engages I would suggest you leak check the system and fix the leak before you recharge it.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: Duracool and AC Compressor Pressure Cut-Off Switch [message #215271 is a reply to message #215269] |
Sun, 21 July 2013 20:54 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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| A Hamilto wrote on Sun, 21 July 2013 18:39 |
| roy1 wrote on Sun, 21 July 2013 20:29 |
The only reason to bypass it is if you are low on refrigerant and adding more to the system. Once there is enough in the system it doesn't need to be jumped. Actually it is really a loss of charge switch. If you jump it and the compressor engages I would suggest you leak check the system and fix the leak before you recharge it.
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With R12, 20PSI IS LOW.
I have to guess that, either the people that have used Duracool do not have a switch, or the switch does not cut off until it gets to something below 20PSI, even though the MM says it shouldn't run below 37 PSI.
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You are confusing the switch with a suction line low pressure switch which the GMC doesn't have. Yes it is a low pressure switch per say but it is located on the high pressure liquid line that is why it would be considered a Loss of charge switch. It only opens when the refrigerant charge is low.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: Duracool and AC Compressor Pressure Cut-Off Switch [message #215278 is a reply to message #215272] |
Sun, 21 July 2013 21:37 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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| A Hamilto wrote on Sun, 21 July 2013 19:05 |
| roy1 wrote on Sun, 21 July 2013 20:54 |
You are confusing the switch with a suction line low pressure switch which the GMC doesn't have. Yes it is a low pressure switch per say but it is located on the high pressure liquid line that is why it would be considered a Loss of charge switch. It only opens when the refrigerant charge is low.
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Ah. I should have read the whole section. A sentence above where I found the 37PSI figure says:
The switch is located in the evaporator inlet line (high pressure).
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Now you got it changes the the thought on the function of a low pressure control.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Duracool and AC Compressor Pressure Cut-Off Switch [message #215816 is a reply to message #215814] |
Fri, 26 July 2013 17:19 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Don't forget that you have a resistor in the blower housing accessable
from the drivers side door below the brake m.c.. The blower motor should
have a bit more resistance than you measured when it is running due to
counter electromotive force or cemf.
Jim Hupy
Salem, Or.
78 gmc royale 403
On Jul 26, 2013 2:31 PM, "A." <markbb1@netzero.com> wrote:
>
>
> A Hamilto wrote on Sun, 21 July 2013 22:09
> > Yep. Got it. When I get the fan working and the AC compressor to
> engage, I will see if the dash air works, or if I need to convert to
> Duracool.
> Progress report. I found the problem. The wire coming off the blower
> relay to the blower has multiple bad connections. The spade connection at
> the relay is corroded, the inline link is corroded, the crimp to the wire
> of the connector that presses into the spade connector was not crimped. I
> have cleaned the connections. As soon as I find my soldering iron, I will
> crimp and solder the crimp connection.
>
> http://gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&goto=180508
>
> Maybe this is why it didn't have dash air.
>
> Does anybody know what the resistance should be across the blower motor?
> It ohms out at about 0.4 ohms, and that would allow so much current that
> the fuse would blow.
> --
> '73 23' Sequoia For Camping
> '73 23' CanyonLands For Sale
> UA (Upper Alabama)
> "Time is money. If you use YOUR time, you get to keep YOUR money."
> _______________________________________________
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