AC pressure on the low side
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Re: AC pressure on the low side (love to drive)
either 12 or 1324 will read real close, on suction-lo side it should be 30-35 lbs pressure...menaing around freezing for temp....as cold as the coil can get without iceing up...
now the hi side will vary quite a bit....only 75-80% of the 12 value will be useable in a 134 charge....134 will rin about 100 lbs higher than 12...
the units really need a larger condensor for 134, but that's the way it goes...
not worth changing condensors over...
GENE
now the hi side will vary quite a bit....only 75-80% of the 12 value will be useable in a 134 charge....134 will rin about 100 lbs higher than 12...
the units really need a larger condensor for 134, but that's the way it goes...
not worth changing condensors over...
GENE
Drifting
Joined: Mar 2001
Posts: 1,514
Likes: 1
Re: AC pressure on the low side (mrvette)
With R134a I have 26# on the low side at 80 ambient temp, and 230# on the high side. That turned out to be the "sweet spot" to get the best vent temp.
What makes you think low pressure, compressor cycling alot or warm air out of vents?
Scott
What makes you think low pressure, compressor cycling alot or warm air out of vents?
Scott
Thread Starter
Instructor
Joined: Aug 2001
Posts: 150
Likes: 0
From: Jacksonville FL
Re: AC pressure on the low side (Scott78)
Actually, I believe my pressure is too high because the compressor will only engage when the car is cold and then it will only stay on for a few minutes. Leads me to believe there is too much pressure causing the compressor's safety valve to activate. With a pressure guage I got a reading of 65+ which seems way too high
Thanks,
Ted
Thanks,
Ted
Drifting
Joined: Mar 2001
Posts: 1,514
Likes: 1
Re: AC pressure on the low side (love to drive)
The pressures posted are with the compressor running. If the compressor isn't running the system will equalize and Hi/Low side pressures will be the same. You need to have the AC running on high max when your doing service dealing with the charge of the system.
AC systems can be potentially dangerous if worked on improperly. I'm not an AC expert by any means. But I did rebuild and charge mine after doing some research.
Scott
[Modified by Scott78, 12:38 PM 7/31/2002]
AC systems can be potentially dangerous if worked on improperly. I'm not an AC expert by any means. But I did rebuild and charge mine after doing some research.
Scott
[Modified by Scott78, 12:38 PM 7/31/2002]
Thread Starter
Instructor
Joined: Aug 2001
Posts: 150
Likes: 0
From: Jacksonville FL
Re: AC pressure on the low side (Scott78)
ahhh that's what I figured. I haven't been able to get the compressor running while testing the system so I don't know for sure. I probably just need a new compressor. I'll check the voltage getting to the compressor tonight though to make sure the switch is working right.
Ted
Ted
Drifting
Joined: Mar 2001
Posts: 1,514
Likes: 1
Re: AC pressure on the low side (Biker)
Can't mix refrigerants. The stuff you can go out and buy now, R134a can't go in an old system without doing a few things. Now there are R12 substitutes out there, but I don't have clue on how good or if they work at all.
I'm pretty happy with the results of the retrofit to R134. More air volume would be nice, so the post on the fan upgrade was timely :yesnod:
Scott
I'm pretty happy with the results of the retrofit to R134. More air volume would be nice, so the post on the fan upgrade was timely :yesnod:
Scott
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Drifting
Joined: Mar 2001
Posts: 1,514
Likes: 1
Re: AC pressure on the low side (love to drive)
ahhh that's what I figured. I haven't been able to get the compressor running while testing the system so I don't know for sure. I probably just need a new compressor. I'll check the voltage getting to the compressor tonight though to make sure the switch is working right.
Scott
Intermediate
Joined: Apr 2002
Posts: 29
Likes: 0
From: Brewster New York
Re: AC pressure on the low side (love to drive)
you can be either under charged or overcharged to have what you describe(65lbs/sqin). When I charge I pull a vac. on the system, bring the engine speed to about 1100-1200rpm which is usually just a dime in the linkage. Then charge slowly just enough refrigerant to keep the compressor running at that RPM. That is the without gauges meathod which has worked without fail.
When charging with gauges watch the pressure and open and close the valve often so you can read the actual pressures on the gauge. read the gauge only when the valve is closed and the compressor is running.
now to answer your pressure question...when charging a refrigerant into the system you have to do it slowly and read the gauge often, the reason for this is that the pressure and temp. corresponds together as you can see on the ref. gauges. This means there will be a point where you are getting the best cooling effect usually corresponding to 36F-38F evaperator temp. When you go past that point it is overcharged increasing the pressure in the system which also causes no cooling effect due to the coresponding rise in temp.
When charging with gauges watch the pressure and open and close the valve often so you can read the actual pressures on the gauge. read the gauge only when the valve is closed and the compressor is running.
now to answer your pressure question...when charging a refrigerant into the system you have to do it slowly and read the gauge often, the reason for this is that the pressure and temp. corresponds together as you can see on the ref. gauges. This means there will be a point where you are getting the best cooling effect usually corresponding to 36F-38F evaperator temp. When you go past that point it is overcharged increasing the pressure in the system which also causes no cooling effect due to the coresponding rise in temp.
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Re: AC pressure on the low side (Scott78)
With R134a I have 26# on the low side at 80 ambient temp, and 230# on the high side. That turned out to be the "sweet spot" to get the best vent temp.
What makes you think low pressure, compressor cycling alot or warm air out of vents?
Scott
What makes you think low pressure, compressor cycling alot or warm air out of vents?
Scott
