AC Problems. R132 present, Clutch Turning, Hot Air.

[glmoore001]

I put the gauges on the system, started the engine. clutch cycles. 75 degrees outside, low side 75 psi, high side about 80 lbs.
Pressure changed very little, needles move very little,, gauges are not cycling.
The system never cools regardless of RPM.
The system is charged, but unknown if there is the correct amount of freon (R132).
How do I tell if this is a Compressor failure, expansion valve failure or a plugged orafice?
I will replace the needed items, but do not want to replace compressor then find out it was the expansion valve.. Thanks.. Gary

 

[Wayne M.]

I really think you have a light charge in there. The only right way to do this is with a charging station. Recover to see how much comes out, then fill it up with the proper oil and proper measure of 134. The machine I use will do a leak test in between recover and charge.

 

[glmoore001]

Thank you for the post Wayne. I could get it recovered then put the recommended oz in the system. Doesn't it normally tell me what my truck is supposed to take on a body tag under the hood somewhere? Thanks.. Gary

 

[petersonj]

Thank you for the post Wayne. I could get it recovered then put the recommended oz in the system. Doesn't it normally tell me what my truck is supposed to take on a body tag under the hood somewhere? Thanks.. Gary

Yes, there should be a sticker near the radiator on the passenger side showing the amount of refrigerant required. My truck is an '02 and it takes 1 lb, 14 oz. Your truck will probably be similar.

- John

 

[fest3er]

75-80 PSI isn't unreasonable if the A/C system is 'at rest'. If the compressor is cycling, you should see the low pressure side decrease to around 25 PSI, the compressor disengage, the pressure rise back to around 40PSI, the compressor engage, and the pressure decrease to about 25 PSI. If the charge is rather low, the compressor should cycle somewhat rapidly (like engage every couple/three seconds). If the charge is too high, you might see the low pressure drop to maybe 30-35 PSI and the compressor not disengage. If the orifice is blocked, you might see the high pressure rise rapily and the low pressure not change much. (If the orifice is plugged up and before the high pressure switch, you might hear some startling noise from the compressor.)

If you hear the compressor clutch cycle but the pressures don't change (as you've observed), I might suspect the clutch is slipping or the compressor isn't compressing.

[Aside and FWIW, I'm still running the original compressor and clutch on my '98. All the problems I had with the A/C over the years stemmed from a leak in the evaporator, probably from the factory. After I replaced that a few years ago, the A/C has been flawless and cold. But it doesn't work very well under 35°F (windows can fog up), probably because I added a couple ounces too much R-134a.]

 

[Wayne M.]

You might be right fest3r, but you have to hit the easy and obvious first. I still think standing pressure at 75f ambient would yield more than what he's saying in a static condition though.

 

[B.G. Smith]

Yes, 80# at 75% would be at or near correct vapor of R-134. If the compressor is actually running you either have bad clutch or bad compressor. bg

 

[glmoore001]

Hmm.. I apparently did not hit the Post Reply button earlier this week when I posted this question.
Is there any easy way to diagnose clutch or compressor failure? The clutch is pulling in and cycling. I have no idea if the compressor is turning under the clutch.
If I can find out one way or another, I will have the R134 recycled and replace the component.
Will there be evidence of the clutch being bad if I remove it?
Can I test the compressor somehow if I remove the belt?
thanks for the help guys!
Gary Moore

 

[DavidC]

You are saying the clutch is cycling which is the low pressure switch. Your gauge on the low side should be going down to 25 - 30

FIXED ORIFICE TUBE
The fixed orifice tube can be checked for proper
operation using the following procedure. However,
the fixed orifice tube is only serviced as a part of the
liquid line unit. If the results of this test indicate
that the fixed orifice tube is obstructed or missing,
the entire liquid line unit must be replaced.
WARNING: THE LIQUID LINE BETWEEN THE CONDENSER
OUTLET AND THE FIXED ORIFICE TUBE
CAN BECOME HOT ENOUGH TO BURN THE SKIN.
USE EXTREME CAUTION WHEN PERFORMING THE
FOLLOWING TEST.
(1) Confirm that the refrigerant system is properly
charged. See Refrigerant System Charge in the Service
Procedures section of this group.
(2) Start the engine. Turn on the air conditioning
system and confirm that the compressor clutch is
engaged.
(3) Allow the air conditioning system to operate for
five minutes.
(4) Lightly and cautiously touch the liquid line
near the condenser outlet at the front of the engine
compartment. The liquid line should be hot to the
touch.
(5) Touch the liquid line near the evaporator inlet
at the rear of the engine compartment. The liquid
line should be cold to the touch.
(6) If there is a distinct temperature differential
between the two ends of the liquid line, the orifice
tube is in good condition. If there is little or no
detectable temperature differential between the two
ends of the liquid line, the orifice tube is obstructed
or missing and the liquid line must be replaced

Dave

 

[glmoore001]

Thank you for the response Dave.That is good information to have.
The clutch is cycling but I am not sure if the compessor is turning or not. Neither gauge, low or high are cycling. They both stay within 5lbs of each other at all times at about 70lbs which if I remember correctly, is about the same as when the compressor is at rest. Gary

 

[Wayne M.]

Thank you for the response Dave.That is good information to have.
The clutch is cycling but I am not sure if the compessor is turning or not. Neither gauge, low or high are cycling. They both stay within 5lbs of each other at all times at about 70lbs which if I remember correctly, is about the same as when the compressor is at rest. Gary

If you can see the face of the compressor pulley and clutch, and if when it's cycling, and that center/ outermost part of the clutch spins and stops with the cycling, the compressor is turning. Unless of course there's an internal failure inside the compressor. Rare though.
Your course of action should be to determine if you have the proper charge, and then the excerpt from DavidC should be followed. If you do those things, I think you'll nail it.

 

[glmoore001]

Ok. That is the information I need. Thanks for the help!

 

[DavidC]

If you find there is an obstruction I believe Auto Zone lends out the machine for back flushing and sells the ingredients. I never used it but it does require some lines to be disconnected so if your there get the o-ring set and you will probably need a new receiver/drier and the tools for the lines.

Dave

 

[fest3er]

If the compressor is compressing, you should hear the engine RPM drop a little when the clutch engages, normally maybe 50-100 RPM, but in your case you might not be able to hear a change in RPM.

 

[B.G. Smith]

Hmm.. I apparently did not hit the Post Reply button earlier this week when I posted this question.
Is there any easy way to diagnose clutch or compressor failure? The clutch is pulling in and cycling. I have no idea if the compressor is turning under the clutch.
If I can find out one way or another, I will have the R134 recycled and replace the component.
Will there be evidence of the clutch being bad if I remove it?
Can I test the compressor somehow if I remove the belt?
thanks for the help guys!
Gary Moore

If the clutch is engaging and disengaging (you can hear/see it operating) then the system is probably doing what it is supposed and you are low on refrigerant. I think you need to check the gauges you are using. Do they snap on to the test ports then you screw the valve down to read the pressure? bg

 

[petersonj]

Do they snap on to the test ports then you screw the valve down to read the pressure?

B.G. Smith, you might be on to something here. My recovery station has those quick couplers with the integrated valves. To open the valves requires turning the knob the opposite direction than you would think - clockwise to open. Once when I was testing a system before recovering the refrigerant, I had the valves closed (thought I had them open). Both high and low pressures read about the same and the AC clutch was cycling. Hmmm... After a few minutes I figured out my error and things began working normally.

So, if this is what is going on for the OP, it could explain his symptoms, and really, he just may have a low charge.

- John

 

[glmoore001]

If you find there is an obstruction I believe Auto Zone lends out the machine for back flushing and sells the ingredients. I never used it but it does require some lines to be disconnected so if your there get the o-ring set and you will probably need a new receiver/drier and the tools for the lines.

Dave

Are you talking about if the orafice is plugged? I have priced the liquid lines and they are not outrageous, I will probably just buy new lines if I think I have a blockage.

 

[glmoore001]

If the clutch is engaging and disengaging (you can hear/see it operating) then the system is probably doing what it is supposed and you are low on refrigerant. I think you need to check the gauges you are using. Do they snap on to the test ports then you screw the valve down to read the pressure? bg

The gauges I am using have a quick disconnect coupler at the ports, nothing to open or close. I have opened and closed the valves at the gauges and nothing changes with pressure in either positionon either side. I have successfully vacuumed, repaired and recharged other systems with this setup before. Those vehicles had an empty, leaking system when I started. This is the first repair for me that actually had a pressure in the system and no cooling.
I could add another can and some florescent dye, but still have no idea how much refrigerant is in there now.
I do not really want to evacuate refill and then find I still have another problem and evacuate again to fix, but I will if that is what I need to do to find the problem.

 

[glmoore001]

If the compressor is compressing, you should hear the engine RPM drop a little when the clutch engages, normally maybe 50-100 RPM, but in your case you might not be able to hear a change in RPM.

You are right, I did not think of this. It should be putting a load on the engine, I do not remember one way or another if this happened. I will check. Thank you.

 

[glmoore001]

If you find there is an obstruction I believe Auto Zone lends out the machine for back flushing and sells the ingredients. I never used it but it does require some lines to be disconnected so if your there get the o-ring set and you will probably need a new receiver/drier and the tools for the lines.

Dave

I would like to change the reciever\dryer but have been told that it is a problem repair. Can anyone tell me if this is true or not. I was told it was a problem removing the connections without damaging them.