1999 Jeep Cherokee 1999 Jeep Cherokee AC cycles on and off

Tiny
FIREDOGUT
  • MEMBER
  • 1999 JEEP CHEROKEE
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
I have a 1999 jeep Cherokee and the AC will blow ice cold for a while then blow warm outside temp air. After a while the AC will blow cold again.

took a it to a shop and here is what they said

"Pressure test a/c system and found no leaks at this time. System is full of r-134a. The a/c compressor clutch is going out on the compressor. Recommend a/c compressor assembly, dryer, liquid line, flush system and fill with R134a"

of course this is not going to be cheap so I took it to a 2nd shop for a 2nd opinion


The 2nd shop stated that he clutch was fine. In fact they stated all the hardware was fine. While trying to figure out what was wrong they evacuate all the refrigerant and added fresh r134a. The tech stated that the older refrigerant was old and had a lot of air mixed in and maybe a little moisture. He also stated that this was causing the system to act like a low charge even though the gauges read the correct pressure. This did sound a little strange and I was given two options. They could put back the old refrigerant or leave the new in and I would have to pay for the evacuate and recharge.


Does this sound like it is possible?
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Friday, July 17th, 2009 AT 6:50 PM

8 Replies

Tiny
SERVICE WRITER
  • EXPERT
Sounds more like he wants this to go away, but get paid for a guess.

Sounds more like a cycling switch problem.
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Friday, July 17th, 2009 AT 7:35 PM
Tiny
RASMATAZ
  • MEMBER
AIR CONDITIONER PROBLEM: INTERMITTENT COOLING

An A/C system that blows cold air for awhile then warm air is probably freezing up. This can be caused by air and moisture in the system that allows ice to form and block the orifice tube.

Evacuating the system with a vacuum pump will purge it of unwanted air and moisture. Evacuation should be done with a vacuum pump that is capable of achieving and holding a high vacuum (29 inches) for at least 30 to 45 minutes.

For best performance, an A/C system should contain less than 2% air by weight. For every 1% increase in the amount of air that displaces refrigerant in the system, there will be a corresponding drop of about one degree in cooling performance. More than 6% air can cause a very noticeable drop in cooling performance, and possibly cause evaporator freeze-up.

Air can get inside a system through leaks, by not evacuating the system prior to recharging it, and/or by recharging the system with refrigerant that is contaminated with air. Recovery equipment can suck air into the recycling tank if an A/C system contains air or if the system has a leak. For this reason, the refrigerant recovery tank on recycling equipment must be checked and purged daily. On some equipment, this is done automatically. But on equipment that lacks an automatic purge cycle, tank pressure and temperature has to be measured and compared to a static pressure reference chart.

Some refrigerant identifier equipment can detect air in the system as well as other contaminants. An identifier should be used to check the refrigerant before the system is serviced to prevent cross-contamination of recovery and recycling equipment.

Possible causes of intermittent cooling in a manual A/C system that might be caused by an electrical problem include:

Faulty low pressure cutout switch. This switch prevents the compressor from running if the refrigerant level is low. If the cutout switch is not reading correctly, it can prevent the compressor from coming on.

Faulty compressor clutch. The magnetic clutch on the compressor requires full battery voltage to engage. If the voltage to the clutch is low, or the clutch coils have too much resistance, or the air gap in the clutch is too great, the clutch may not engage to drive the compressor.

Faulty compressor clutch relay. Check to see if the relay is receiving voltage when the A/C is turned on. Also check the relay wiring and ground connections. If bypassing the relay with a jumper wire or routing battery voltage directly to the compressor clutch makes the A/C work, the relay is probably bad.

Faulty A/C control switch. The switch may be worn and not making good contact when it is turned on.

Some possible causes of intermittent cooling (or no cooling) on automatic A/C systems include all of the above, plus:

A problem in the control module or control head (this usually requires using a dealer scan tool to read fault codes and perform self-diagnostics).

A bad temperature sensor (an ambient air temperature sensor, interior air temperature sensor, evaporator temperature sensor, or sunload sensor). Again, a factory scan tool is usually required to perform diagnostics on the system.
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Friday, July 17th, 2009 AT 7:36 PM
Tiny
FIREDOGUT
  • MEMBER
So my question is still there. If I did have to much air mixed with the r134a would I have these issues.

We did have him leave the new r134a in the system. And paid him for that and the vacuum. It has been 24 hours and the car has been driven 40 miles (20 miles each way)

The AC was left on high the whole time and never cut off. Where before it would cut off after 5-10 min

I want to make sure that this is not some temporary fix. Like I said both stated no leaks.
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Friday, July 17th, 2009 AT 9:48 PM
Tiny
RASMATAZ
  • MEMBER
They probably didn't evacuate the system properly-one of those components that I've mentioned earlier is causing the problem-they need to check it step by step.
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Friday, July 17th, 2009 AT 11:40 PM
Tiny
FIREDOGUT
  • MEMBER
What makes you say that?
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Saturday, July 18th, 2009 AT 8:35 AM
Tiny
RASMATAZ
  • MEMBER
I have a 1999 jeep Cherokee and the AC will blow ice cold for a while then blow warm outside temp air. After a while the AC will blow cold again.

XXXXXX An A/C system that blows cold air for awhile then warm air is probably freezing up. This can be caused by air and moisture in the system that allows ice to form and block the orifice tube.

Evacuating the system with a vacuum pump will purge it of unwanted air and moisture. Evacuation should be done with a vacuum pump that is capable of achieving and holding a high vacuum (29 inches) for at least 30 to 45 minutes. XXXXXX
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Saturday, July 18th, 2009 AT 10:05 AM
Tiny
FIREDOGUT
  • MEMBER
Do you have to evac the system to replace the clutch switch? (Low Pressure Cycling Switch)

what about the high pressure?

You should be able to replace either switch with a system that is charged because you never open the system. Correct?
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Tuesday, July 21st, 2009 AT 5:49 PM
Tiny
RASMATAZ
  • MEMBER
You should be able to replace either switch with a system that is charged because you never open the system. Correct?

You didn't open the system-
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Tuesday, July 21st, 2009 AT 7:34 PM

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