A/C problem

htseat2000

Original poster
Member
Jan 25, 2013
62
I have a problem with my a/c. it happened last year one time and is happening this year more often. yesterday when we went on a 2 hour road trip, I turned on the a/c no problems, it got cool, then all of sudden started blowing luke cold air, then all of the sudden it would get cold again, then started blowing luke cold air again, and did so till we stopped at a gas station. I popped hood and saw that the compressor was not running. I jiggled the what I thought was the low pressure switch connection and it kicked back on. system has plenty of Freon in it. just wondering if the pressure switch could be the problem as to why it kicking on and off so much. or is my a/c compressor on the fritz? I might also need to let some Freon out of the system too because I think pressure is a little too high. is there an easy way to do that also?
 

meerschm

Member
Aug 26, 2012
1,079
it is normal for the low pressure switch to turn off and on, depending on conditions and engine speed.

it is also somewhat common for the low pressure switch to get flaky, and since it is not too expensive, and can be changed without opening up the refrigerant loop, is a common guess. if you can wiggle, tap, or look at sideways the low pressure switch and get a non-moving compressor clutch to engage, you could try to change out the low pressure switch. it mounts on a schrader valve, like the one you use to put air in the tires

Why do you think the system may have too much r134a?

the only way to really adjust the amount of 134a is to use a recovery system to pump out and pull a vacuum on the system, and load by weight.
 

htseat2000

Original poster
Member
Jan 25, 2013
62
meerschm said:
it is normal for the low pressure switch to turn off and on, depending on conditions and engine speed.

it is also somewhat common for the low pressure switch to get flaky, and since it is not too expensive, and can be changed without opening up the refrigerant loop, is a common guess. if you can wiggle, tap, or look at sideways the low pressure switch and get a non-moving compressor clutch to engage, you could try to change out the low pressure switch. it mounts on a schrader valve, like the one you use to put air in the tires

Why do you think the system may have too much r134a?

the only way to really adjust the amount of 134a is to use a recovery system to pump out and pull a vacuum on the system, and load by weight.

why I think I have too much in the system is because when I hooked the gauge up it was borderline green/red on the gauge. don't remember what psi it was. I think maybe the low pressure switch is what is getting flaky because it kicks on and freezes you out and the next thing you know it is blowing out luke warm air and then after a bit, it freezes you out again.
 

meerschm

Member
Aug 26, 2012
1,079
really hard to tell anything with a single gauge. (except that there is some r134a in the system, and if the pressure goes up and down that the compressor is doing something and if you can hear the switch click on and off that the switch works (pressure would lower till the switch clicks then come back up while the compressor is off.)

ambient low pressure in operation varys quite a bit with temp and humidity.

with a dual high/low gauge set, you can have more insight. my system cycles on and off when it is 70f, but over 80 f it stays pretty much steady on at engine idle.

there are plenty of things which could be causing problems.

best bet really is to take it to a place for diagnosis.


if you can tap or jiggle the low pressure switch and it kicks in, you can replace the switch.

only benefit of this is is is not too expensive and might be the issue. then again, it might be somthing else.
 

meerschm

Member
Aug 26, 2012
1,079
it also could be that it has too little r134a installed.

again, the only way to do this correctly is to use a recovery system, pull a vacuum, and fill by weight.
 

CaptainXL

Member
Dec 4, 2011
2,445
Filling by weight is for the initial fill. You can then adjust by high and low pressure after than. There should be no reason to drain the entire system just to add refrigerant.
 

meerschm

Member
Aug 26, 2012
1,079
xcept if it is leaking, you really should fix the leak. and to do this you really should recover the r134a.



also have to be very careful adding r134a. don't want to get too much in, bad things can happen. (like my neighbor who blew a hose)

even if you load by weight, you probably want to watch pressures, could be more oil (including leak check dye or stop-leak) than specified, which would reduce the capacity of the system.
 

CaptainXL

Member
Dec 4, 2011
2,445
My compressor and fan clutch is working just fine. Pressures are also in the right range. Compressor clutch works beautifully.

Now! Here is the kicker. I just found out that the problem might be the actuators. I have a few videos that I would like to post to show you guys. Very interesting conclusions. Also very perplexing. Stay tuned.
 

meerschm

Member
Aug 26, 2012
1,079
good news is you do not have to weigh the actuators.

:thumbsup:
 

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