A/C help with 90 XJ ...
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Joined: Sep 2009
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From: Edmonton, Alberta
Model: Cherokee
A/C help with 90 XJ ...
I had the dealer retro fit my system to 134A. Recharged and checked for leaks. All OK. Although, there is a problem he diagnosed as the "A/C clutch not engaging" and is probably a part (description not given) that is located under dash passenger side.
I have noticed over the years of some kind of vacuum switch that only works when the outside temp is cold and then the A/C works. When it is hot out, this switch doesn't work and no A/C. What is the proper description of this part and how difficult is it to be installed?
I have noticed over the years of some kind of vacuum switch that only works when the outside temp is cold and then the A/C works. When it is hot out, this switch doesn't work and no A/C. What is the proper description of this part and how difficult is it to be installed?
Last edited by robinz; May 10, 2012 at 07:21 PM.
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Joined: Dec 2010
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From: Missouri
Year: 1998
Model: Cherokee
Engine: I6 4.0 L
Originally Posted by robinz
I had the dealer retro fit my system to 134A. Recharged and checked for leaks. OK. Although, there is a problem he diagnosed as the A/C clutch not engaging and is probably a part (description not given) that is located under dash passenger side.
I have noticed over the years of some kind of vacuum switch that only works when the outside temp is cold and then the A/C works. When it is hot out, this switch doesn't work and no A/C. What is the proper description of this part and how difficult is it to be installed?
I have noticed over the years of some kind of vacuum switch that only works when the outside temp is cold and then the A/C works. When it is hot out, this switch doesn't work and no A/C. What is the proper description of this part and how difficult is it to be installed?
Thread Starter
Junior Member
Joined: Sep 2009
Posts: 60
Likes: 1
From: Edmonton, Alberta
Model: Cherokee
Getting back to the A/C, I discovered an overlooked, hand written note on my invoice stating "heater control, $188". Does this make sense? If I can do this work myself I'll probably save myself from another $500 bill.
I've attached a vacuum schematic for a visual aid;
Last edited by robinz; May 10, 2012 at 07:22 PM.
Thread Starter
Junior Member
Joined: Sep 2009
Posts: 60
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From: Edmonton, Alberta
Model: Cherokee
Found this link exactly describing my problem.
http://www.fixyourboard.com/techzone...g/jeep_ac.html
Excessive clutch airgap on compressor.
Quote: "At high ambient temperatures, when the engine gets hot, the IR copper losses in the clutch winding increase, thereby reducing the clutch current and the magnetic force. This magnetic force drops low enough to release the clutch even though there is current in the winding. On cooler days, or more airflow (high speed), or before the engine reaches max temperature, there is enough magnetic force to engage the clutch and things work fine."
Seems like a little out of my league to follow up on.
http://www.fixyourboard.com/techzone...g/jeep_ac.html
Excessive clutch airgap on compressor.
Quote: "At high ambient temperatures, when the engine gets hot, the IR copper losses in the clutch winding increase, thereby reducing the clutch current and the magnetic force. This magnetic force drops low enough to release the clutch even though there is current in the winding. On cooler days, or more airflow (high speed), or before the engine reaches max temperature, there is enough magnetic force to engage the clutch and things work fine."
Seems like a little out of my league to follow up on.
Thread Starter
Junior Member
Joined: Sep 2009
Posts: 60
Likes: 1
From: Edmonton, Alberta
Model: Cherokee
Thank you freegdr for your input. I did consider the heater control valve but the symptoms just don't convince me. Everything works fine until the engine bay heats up. I'll look into it though. I see that on ebay I can get a replacement compressor for around $100 delivered. I'm pondering.
You'd think with over 20 years of field testing of XJ's and the numerous years of experience of the members here one would get more response. I'm disappointed.
You'd think with over 20 years of field testing of XJ's and the numerous years of experience of the members here one would get more response. I'm disappointed.
Last edited by robinz; May 13, 2012 at 09:40 PM.
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