A/C Troubleshooting Question - JeepForum.com
 1Likes
  • 1 Post By funtapaz
 
LinkBack Thread Tools
post #1 of 11 Old 04-05-2017, 09:44 PM Thread Starter
funtapaz
Registered User
1999 XJ Cherokee 
 
Join Date: Apr 2017
Posts: 20
A/C Troubleshooting Question

So the A/C has been out on my 99 XJ 4.0 for a few years now. I'd never really bothered to get it fixed as I was unsure for a long time about whether or not I wanted to keep the vehicle. Last fall I took it to a garage and had them take a look at it, they didn't give me details, but said they'd need to replace the entire system because the compressor was shot. I put off the work until spring because of the hefty price tag.

Now spring is here, and I'm looking at my options. Interestingly enough, I turned the A/C on yesterday on a whim from a cold start. It worked amazingly! Pushed ice cold air. I popped the hood and noticed the clutch was fully engaged, and then it disengaged after a few minutes. Naturally this sent me into an investigative hustle and I ended up snooping around online and using my noggin a little. Here's what I've checked so far.

  • Condenser fan: Works fine
  • Compressor Fuse: Good
  • Compressor Relay: Good
  • Low pressure switch line voltage with A/C on full blast: ~4mV
  • Clutch coil wiring: ~13V with A/C on
  • Measured impedance of the coil is 3.3 ohms (read normal can be anywhere between 2-5 ohms depending on compressor model/vehicle)
  • Clutch face attracts steel with A/C on
  • Jumping low pressure switch results in 13V to coil wiring, but no engagement.
  • Inner clutch face can be moved by hand with relative ease. No nasty sounds or rough feelings.

I wanted to check the pressure, but it seems the compressor needs to actually be running for that. No garage has claimed it had any leaks during past service checks, as well as the latest check last fall.

I'm starting to lean toward the only issue being that the electromagnet in the clutch has weakened enough to prevent engagement after 18 years and 200,000 miles. Would anyone have any further troubleshooting advice to help confirm my suspicions?

funtapaz is offline  
Sponsored Links
Advertisement
 
post #2 of 11 Old 04-06-2017, 01:50 AM
oIIIIIooIIIIIo
Registered User
1988 MJ Comanche 
 
Join Date: May 2013
Location: bountiful
Posts: 83
That's what I would say, or you could a wiring issue, which can be more aggravating to trace down. You can replace just the clutch . A clutch is about $70 for that vs over $100 and replacing the coolant.
The fact that it worked , intermittently, would indicate the system overall is good.


Sent from my iPhone using Tapatalk
oIIIIIooIIIIIo is offline  
post #3 of 11 Old 04-06-2017, 01:59 AM Thread Starter
funtapaz
Registered User
1999 XJ Cherokee 
 
Join Date: Apr 2017
Posts: 20
Quote:
Originally Posted by oIIIIIooIIIIIo View Post
That's what I would say, or you could a wiring issue, which can be more aggravating to trace down. You can replace just the clutch . A clutch is about $70 for that vs over $100 and replacing the coolant.
The fact that it worked , intermittently, would indicate the system overall is good.


Sent from my iPhone using Tapatalk
The measurements for voltage to the coil were taken as close to the coil itself as I could safely manage. As far as I can tell the low pressure switch is constantly turning on the relay telling the coil to pull the clutch in, but the engagement just isn't happening.
funtapaz is offline  
 
post #4 of 11 Old 04-06-2017, 09:03 AM
CCKen
Web Wheeler
 
CCKen's Avatar
1999 XJ Cherokee 
 
Join Date: Jul 2011
Location: Canton
Posts: 3,548
Here's some AC Compressor Clutch tests you can perform. They may not be conclusive but worth a try.

Bit of a walk around:


.
Compressor Clutch Ground Test:


.
Compressor Clutch Resistance Test (can be performed with the Compressor installed in the Jeep - bench test shown):


.
CCKen is offline  
post #5 of 11 Old 04-06-2017, 02:50 PM Thread Starter
funtapaz
Registered User
1999 XJ Cherokee 
 
Join Date: Apr 2017
Posts: 20
So considering all tests are pointing to the coil being weak, what should I do? The pulley seems fine, and the clutch itself seems to engage no problem if it's under 75F surface temperature. Just get a new coil, or replace the entire assembly?
funtapaz is offline  
post #6 of 11 Old 04-07-2017, 12:10 AM
rep-tile
Cash 4 Clunkers Survivor
 
rep-tile's Avatar
2004 WJ 
 
Join Date: Jul 2013
Location: bakersfield
Posts: 1,456
You don't mention anything about testing the high pressure switch. That's the one that kills the compressor if pressure is too high on the high side.

You can actually bypass everything by supplying +12V to the compressor's connector directly from the battery pos. (ground is already provided by the engine if it's a 1 wire connector). I would not attempt without a set of pressure gauge and closely monitor the pressure. If your orifice tube happens to be clogged and you let it build too much pressure, something is going to blow and you want to be nowhere near it.

04 WJ 4.0 - Avital 4103, DB-ALL
91 XJ 4.0 - Avital 4103, Stage-2 aFe intake system, BBK high flow Throttle Body, Jones Exhaust A3518M-5
rep-tile is offline  
post #7 of 11 Old 04-07-2017, 01:17 AM Thread Starter
funtapaz
Registered User
1999 XJ Cherokee 
 
Join Date: Apr 2017
Posts: 20
Quote:
Originally Posted by rep-tile View Post
You don't mention anything about testing the high pressure switch. That's the one that kills the compressor if pressure is too high on the high side.

You can actually bypass everything by supplying +12V to the compressor's connector directly from the battery pos. (ground is already provided by the engine if it's a 1 wire connector). I would not attempt without a set of pressure gauge and closely monitor the pressure. If your orifice tube happens to be clogged and you let it build too much pressure, something is going to blow and you want to be nowhere near it.
The compressor will run fine until the surface temp of the clutch reaches ~75F. The clutch coil is being supplied 12V, attracts steel, and the the low pressure switch is telling the clutch to engage, but it fails to pull it in after that temperature is reached. The compressor will cycle normally for as long as needed until the clutch gets warm. The coil's resistance is 3.3ohms, which is definitely way below the normal range given in the images above.
funtapaz is offline  
post #8 of 11 Old 04-07-2017, 07:45 AM
CCKen
Web Wheeler
 
CCKen's Avatar
1999 XJ Cherokee 
 
Join Date: Jul 2011
Location: Canton
Posts: 3,548
Quote:
Originally Posted by funtapaz View Post
The compressor will run fine until the surface temp of the clutch reaches ~75F. The clutch coil is being supplied 12V, attracts steel, and the the low pressure switch is telling the clutch to engage, but it fails to pull it in after that temperature is reached. The compressor will cycle normally for as long as needed until the clutch gets warm. The coil's resistance is 3.3ohms, which is definitely way below the normal range given in the images above.
The clutch is shot.

It can be replaced if you can find one.

You may be better off replacing the AC Compressor assembly.

If you go this route note that the new compressor warranty paperwork may want you to replace the Liquid Line and the Accumulator.
CCKen is offline  
post #9 of 11 Old 04-07-2017, 01:51 PM Thread Starter
funtapaz
Registered User
1999 XJ Cherokee 
 
Join Date: Apr 2017
Posts: 20
Quote:
Originally Posted by CCKen View Post
Quote:
Originally Posted by funtapaz View Post
The compressor will run fine until the surface temp of the clutch reaches ~75F. The clutch coil is being supplied 12V, attracts steel, and the the low pressure switch is telling the clutch to engage, but it fails to pull it in after that temperature is reached. The compressor will cycle normally for as long as needed until the clutch gets warm. The coil's resistance is 3.3ohms, which is definitely way below the normal range given in the images above.
The clutch is shot.

It can be replaced if you can find one.

You may be better off replacing the AC Compressor assembly.

If you go this route note that the new compressor warranty paperwork may want you to replace the Liquid Line and the Accumulator.
I've managed to find a clutch kit for about $80 on eBay. I'll update with how it goes once I get the parts swapped. Thanks a lot for the help so far by the way.
CCKen likes this.
funtapaz is offline  
post #10 of 11 Old 04-09-2017, 10:06 AM
john NC
Registered User
 
john NC's Avatar
2000 XJ Cherokee 
 
Join Date: Apr 2007
Location: Corolla
Posts: 1,417
i fixed mine a few years ago by removing a shim from behind the clutch. (i think, it was a while ago) worked until the compressor seized and i just took the damn thing out and installed a $30 bypass pulley

00 XJ - missing lots of sheet metal

RIP: 05 TJ
john NC is offline  
post #11 of 11 Old 04-12-2017, 07:03 PM Thread Starter
funtapaz
Registered User
1999 XJ Cherokee 
 
Join Date: Apr 2017
Posts: 20
Got it working! Just replaced the hub and the magnet. Cleaned up the pulley, and the original bearing was still smooth and sealed. As you can see from the picture here, they definitely needed to be replaced.

At least I'll get to avoid the back sweat this summer.
Attached Thumbnails
IMG_20170411_155805_1492045360195.jpg  
funtapaz is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may 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 On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome