A/C pressure fluctuates.

Reply

  #1  
Old 04-25-10, 07:08 AM
Member
Thread Starter
Join Date: Apr 2010
Location: US
Posts: 7
Question A/C pressure fluctuates.

Hi everyone, I have a Jeep Grand Cherokee 95. I recently charged it and now the pressure gauge reading fluctuates between 25-40 psi. The only problem is that the pressure goes up to 40 psi then the clutch disengages, in about three seconds the pressure drops to 25 psi and the clutch engages until the pressure gets to 40 psi (it takes about three to get to 40 psi). And this goes on and on.

I am not sure if this is a normal, on my other tuck the pressure does not fluctuate at all, it just stays on 35 psi.

Thank you for your advice and help in advance,

-Jay
 
Sponsored Links
  #2  
Old 04-26-10, 12:32 AM
Join Date: Jul 2009
Location: Washington State
Posts: 312
Is that the high or low side reading? Need to know to help more if low side whats the high sides read if that is the high side,I'd have to say not enough refrigerant in the system yet for starters.
That one takes 1.75 lbs R134 and 8 oz pag oil
 
  #3  
Old 04-26-10, 05:16 AM
Member
Thread Starter
Join Date: Apr 2010
Location: US
Posts: 7
Hi Maniac Mechanic,

Thank you for trying to help. I only have the low side gauge; all the readings are from the low side.

Thank you,

-Jay
 
  #4  
Old 04-26-10, 11:01 PM
Join Date: Jul 2009
Location: Washington State
Posts: 312
Ok Will shoot from the hip, The problem is on your high side pressure or related high side pressure switch. IF you have the proper amount of R134 in there You are either dealing with a plugged/blocked orifice tube,evaporator causing the high side pressure to get too high and shutting down the ac system till the pressure balances back to the low side where it comes back on. I don't think you have a condenser problem due to the low side staying about where it should be.(would drop as the compressor runs)The second is a bad high side pressure switch.Don't think the issue is in the low side switch because it opens when in a low pressure situation(below 15 on the low side) the high side switch opens when above 250 to 300 but otherwise is closed.
Hope that helps you
Good Luck
It would help to know high side pressure to confirm this though
 
  #5  
Old 05-03-10, 05:54 PM
Member
Thread Starter
Join Date: Apr 2010
Location: US
Posts: 7
Unhappy

Hi Maniac Mechanic,

I was able to obtain a manifold gauge and take some measurements, initially it appeared that I needed more R134 so I added two cans.

Now I have: Low=59, High=270. The pressure fluctuation stopped when the Jeep is idling. The A/C appeared to blow cool air.

When I start driving the Jeep for about 3min the clutch starts to disengage and the cooling stops.

I am not sure if I need more R134 considering that when I took the reading it was about 80-85F outside.

Please help.

-Jay
 
  #6  
Old 05-03-10, 06:53 PM
Join Date: Jul 2009
Location: Washington State
Posts: 312
Hate to tell ya but think you now have too much in the system if you were using 16 oz cans you now have about 3 lbs in a 1.75 lb system. Both pressures are too high now ,low side should run around 35 to 45 psi and high side 150 to 200 (can be as low as 125) your high side switch is shutting the a/c system down on a good note you know the switches are working properly.A good test to verify your not getting a condenser problem is set your control to max a/c have the windows open and run a water hose in front of the radiator with the hood open watch your compressor it should be running at all times also if you have the elec fan it should be on all the time as well.But feel you now went from undercharged to overcharged.
Good Luck
Will keep an eye out for more posts
 
  #7  
Old 05-12-10, 09:05 PM
Member
Thread Starter
Join Date: Apr 2010
Location: US
Posts: 7
Hi Maniac Mechanic,

I finally was able to locate the problem. After following your instructions and charging it correctly it did not make any sense why the system kept shutting down. So I took my millimeter and started to test the connection 12v to the compressor. It became clear very quickly that the problem was in the snap-in connection.

The ironic part was that I was going to take it to the pros at noon, so I decided to give it my last try in the morning. . . . persistency pays off after all.

Anyhow, I just wanted to tall you my story and also thank you for your help. Without your advice I would have giving up before getting to the bottom of this.

Beer 4U2
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
'