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Unread 05-17-2015, 09:40 AM   #1
300cpilot
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Vacuum lines and A/C issues

1995 XJ 270k miles, to many new parts to list.

I had the A/C compressor replaced yesterday and the A/C does not get a signal to engage the clutch. They found that the vacuum tank behind the bumper had a crack in it so they cut the line feeding it and plugged it. This made the heater/AC controls work properly. I will replace the tank later.

There was a vacuum diagram that someone posted a while back but I was unable to locate it. Was trying to determine if there were other lines from the tank. I could not see any other vacuum lines leaving the tank. I also traced the hoses and found no other cracks/breaks.

They replaced the relay and fuses for the A/C.

But still no signal. Any idea's?
Thanks for your help!

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Unread 05-17-2015, 10:49 AM   #2
shaggyy98
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Does the solenoid engage if you manually apply power to it? Does the system have a full charge of gas? Could be the low pressure switch is malfunctioning if the answer is yes to both the questions.
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Unread 05-17-2015, 11:30 AM   #3
CCKen
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Quote:
Originally Posted by 300cpilot View Post
1995 XJ 270k miles, to many new parts to list.

I had the A/C compressor replaced yesterday and the A/C does not get a signal to engage the clutch. They found that the vacuum tank behind the bumper had a crack in it so they cut the line feeding it and plugged it. This made the heater/AC controls work properly. I will replace the tank later.

There was a vacuum diagram that someone posted a while back but I was unable to locate it. Was trying to determine if there were other lines from the tank. I could not see any other vacuum lines leaving the tank. I also traced the hoses and found no other cracks/breaks.

They replaced the relay and fuses for the A/C.

But still no signal. Any idea's?
Thanks for your help!
Open this link. There's a schematic of the vacuum system in that bunch of pics.

http://www.cherokeeforum.com/g/album/3212409

Click the image to make it larger, click again to make it larger yet.
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Unread 05-18-2015, 09:23 AM   #4
300cpilot
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The system is full and does work if you manually apply power at the relay. If it is the low pressure switch they will have to pull the freon out again, fun stuff. I will ask them to test it. Thanks Ken that was exactly what I was looking for! The diagram only has one tube going to the reservoir so I am good to have it blocked off, until I can get a replacement.
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Unread 05-18-2015, 10:04 AM   #5
CCKen
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Quote:
Originally Posted by 300cpilot View Post
The system is full and does work if you manually apply power at the relay. If it is the low pressure switch they will have to pull the freon out again, fun stuff. I will ask them to test it. Thanks Ken that was exactly what I was looking for! The diagram only has one tube going to the reservoir so I am good to have it blocked off, until I can get a replacement.
You don't have to pull down the refrigerant charge to replace the low pressure cycling switch. The valve in the AC Accumulator will automatically close when the switch is removed,
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Unread 05-18-2015, 10:21 AM   #6
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The '95 XJ has a Fin Sensing Cycling Switch that has a probe that protrudes into the Evaporator fins. It cycles the compressor clutch on and off to prevent condensate water on the Evaporator from freezing.

If the switch goes south it may be preventing the compressor from engaging.

As I recall, these fin switches are hard to find, and a PITA to change.
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Unread 05-18-2015, 03:34 PM   #7
300cpilot
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Dealer says they are not available... Tearing the dash apart is not what I am looking forward to, can you test it without taking it out?
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Unread 05-18-2015, 05:38 PM   #8
CCKen
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Do you have a (Dealer) Factory Service Manual?

If not, you can buy one for $7.95 at Pacific Coast Manuals.com. It's a pdf download.

It will give you the testing procedures and the R&R procedures, if need be.
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Unread 05-18-2015, 05:45 PM   #9
300cpilot
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Yes I have the service manual, it is lacking in ways of testing this, without tearing the dash apart. I was fishing for shortcuts.
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Unread 05-18-2015, 05:53 PM   #10
CCKen
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Quote:
Originally Posted by 300cpilot View Post
Yes I have the service manual, it is lacking in ways of testing this, without tearing the dash apart. I was fishing for shortcuts.
It's in the '95 FSM that I have. The problem I have is the pdf version I have won't let me copy the text from the manual. so I would have to print the page, scan it, load it in my PC, load it in my Photobucket account, then paste it here.

Now.....are you sure you can't afford $7.95 to get a genuine FSM from Pacific Coast Manuals?

BTW, the part number of that Thermostat Control is 55035503. Used in 94-96 XJ's, and probably other Jeep types.
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Unread 05-18-2015, 09:19 PM   #11
300cpilot
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No worries I found it Ken. Thank you for your help Ken and Shaggy!

It was in the form of a 1996 jeep that was sitting beside it. Although this is not an apple to apple comparison it worked out in the end.

According to my manual the A/C system between the two have the same electrical components, however there are some differences. So I disconnected the batteries and went to measuring. Nothing measured the same, even the Fin Sensing Cycling Switch seamed to be different on the ohm meter.

Then I noticed that there were more than one circuit coming off of the 15 amp fuse labeled ignition in the manual. The manual is tuff to follow sometimes. I thought it was funny to label it "Ignition" that when it powered a bunch of stuff, none of which is the ignition system. Then checking the fuse I found it was blown, funny I thought that the guys putting the compressor on surely would have found it. So I put a new one in and when I turned the key to run it exploded, one of the more impressive lights I have seen from a fuse. So then I put a test light in it and begun searching for the short. The whole time I was eyeing the NSS bypass switch I have installed. Went to everything else and noting turned the test light out. So I unplugged the NSS and the light went out. I plugged it back in, started the jeep, unplugged it and put the fuse in and everything works. A/C blows cold, Aux fan kicks on, ****. (Insert Favorite four letter word here!)Shot myself in the foot!



On another note I was told to open the ECM case and see if it was burned, thinking it was the problem. The ECM has a single circuit board in it and it is sealed in about 1/2" of epoxy. The problem is that it is cracked all the way down to the board. Can you reseal the epoxy somehow?
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Unread 05-20-2015, 01:33 PM   #12
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Also an fyi, that "Ignition" labeled fuse also runs the wiper pump + wiper fluid level indicator and the cruse control. Was fun to mark them off the to be fixed list!
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Unread 05-20-2015, 02:41 PM   #13
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Also an fyi, that "Ignition" labeled fuse also runs the wiper pump + wiper fluid level indicator and the cruse control. Was fun to mark them off the to be fixed list!
Amazing.

Help yourself to a cookie, you deserve it.

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