A/C Help
Thread Starter
|
Posting Guru
Joined: Dec 2009
Posts: 2,265
Likes: 2
From: Garden City, KS
A/C Help
Alright, been awhile since I've been on, but I need the help of those of you who know this stuff. Here's the deal: truck was "supposedly" recharged and "supposedly" had dye put in with the freon. The compressor will NOT stay engaged... it does this in A/C or defrost (not sure if that says anything). I've looked all over everything with a black light and couldn't see any leaks that would cause the compressor to stop staying engaged in less than a week. If it was leaking that bad, seems to me the leak would be pretty obvious. Everything in the system was replaced! The thing is, when I bypassed the low pressure switch it cooled down pretty good. So, here's my thinking: would it cool down to the 40's and 50's if it had a low charge? What about shimming the clutch? I've heard of that... I have access to gauges, vacuum pump, freon, whatever I need to do the job. Can I get enough info from watching the gauges to know if I still have plenty of charge and my switch is bad? Am I just gonna have to break the system and start from square one again? I mean, it's only $20 of freon!
So yeah, if any of y'all know something about A/C, I'd be interested in giving you a holler... I'd like to get this fixed before the summer sets in because I have a LONG trip in August that I really don't wanna have screwy A/C when I take it.
So yeah, if any of y'all know something about A/C, I'd be interested in giving you a holler... I'd like to get this fixed before the summer sets in because I have a LONG trip in August that I really don't wanna have screwy A/C when I take it.
Cargo Master
Joined: Sep 2007
Posts: 2,624
Likes: 7
From: OR and UT
Lead Driver
Joined: Sep 2007
Posts: 8,180
Likes: 669
From: Scio, OR
I'm not an expert by any means, but it seems to me that if you bypassed the cycling switch (low pressure switch) and it cooled down, you should have a good charge. You could bypass the switch with a manifold gauge set on and see if you get the right pressures. If you do, and the clutch engages and disengages properly, then it seems like the problem would be the cycling switch.
Fleet Mechanic
Joined: Feb 2006
Posts: 1,776
Likes: 5
From: Lorain County, Ohio
What do you mean by "it won't stay engaged"?
Does the clutch disengage then not re-engage or does it cycle on and off?
To test the system:
-Connect your gauges
-Set the AC on MAX.
-Set the blower to high
-Set the engine speed to 12-1500RPM
-Open the doors fully.
With the compressor running:
- The HIGH side pressure should be about 2.5 times the ambient temperature.
-The LOW side pressure should read in the low 30s.
-The compressor should cycle off when the low side approaches about 26-28psi then it should cycle back on at about 45psi.
If the compressor is cycling at different pressures, the cycling switch is likely bad.
If the cycling occurs quickly within those Low side readings, you are low on refrigerant.
Compressor shaft seal leaks often don't show oil/dye until you remove the clutch plate.
An evaporator leak may not show oil/dye unless you open up the evaporator case. You cna probe the evaporator drain tube with a cotton swab and hit it with a black light to look for dye traces.
Does the clutch disengage then not re-engage or does it cycle on and off?
To test the system:
-Connect your gauges
-Set the AC on MAX.
-Set the blower to high
-Set the engine speed to 12-1500RPM
-Open the doors fully.
With the compressor running:
- The HIGH side pressure should be about 2.5 times the ambient temperature.
-The LOW side pressure should read in the low 30s.
-The compressor should cycle off when the low side approaches about 26-28psi then it should cycle back on at about 45psi.
If the compressor is cycling at different pressures, the cycling switch is likely bad.
If the cycling occurs quickly within those Low side readings, you are low on refrigerant.
Compressor shaft seal leaks often don't show oil/dye until you remove the clutch plate.
An evaporator leak may not show oil/dye unless you open up the evaporator case. You cna probe the evaporator drain tube with a cotton swab and hit it with a black light to look for dye traces.
Elder User
Joined: Dec 2004
Posts: 819
Likes: 3
From: Putnam Valley, New York
A/C
40-50 degrees is not very cold for an A/C system. Mine cools down to 38 degrees coming out of the center outlet, even on an 85 degree day. When it was first charged, did the compressor stay engaged ??? If so, I think you lost most of your charge.
RON
Elder User
Joined: Dec 2004
Posts: 819
Likes: 3
From: Putnam Valley, New York
WARM A/C
You either have a control
head problem or the blend motor for the right side has gone bad.
