I have a 1998 XJ Sport Straight 6 4.0L. The AC isn’t working. I refilled the refrigerant (it was empty) and got a low pressure switch that it was missing. The compressor clutch isn’t engaging at all. I read online that some people have put a 15 Amp fuse in the #10 spot in the fuse box on the passenger side floor and that had somehow fixed their issues. I opened mine up and there was already one in it. I pulled it, looked at it, it was fine so I put it back in and then I heard a click. I had someone come out to see what was happening while I moved the fuse around trying to get a connection. I had them film it and it was the clutch engaging for a second and then disengaging. What could this mean? Do I have a short somewhere? My phone didn’t want to upload the video so I uploaded it to YouTube. Here’s the link.

 

Put a VOM on the clutch supply wire,, are you getting 12v ?
That will narrow it down if it is the supply/control wiring or the clutch it's self

 

Photograph the slot where that fuse goes. Sometimes the contacts become spread and you don't get a decent connection. What are the Ohms across the fuse?
Ensure that the connectors for the low pressure switch and compressor are very secure/solid.

 

 

Where is that wire located?

 

Aside from potential electrical issues - did the new refrigerant stay in the AC system? Did you check pressure with a gauge set? If the system was totally empty with no residual pressure that could indicate a major leak somewhere. Also if exposed to atmosphere the drier should be replaced and vacuum pulled if it hasn't been done.

 

The refrigerant I bought had UV dye in it so if it was leaking anywhere I would be able to see it. So far, I haven’t seen any of it leak anywhere. The refrigerant also came in a can equipped with a pressure gauge on it. When I read it it said there was little to no pressure in the system.

 

The low pressure switch in the system will de-energize the AC compressor clutch if it does not see pressure. The fuse movement is simply making/breaking the circuit by moving the fuse and the momentary clicking noise is the AC compressor clutch energizing and then being de-energized by the low pressure switch. Confirm this by leaving the fuse installed and using your normal system controls to switch on the system. The clutch will momentarily energize and then de-energize by command of the low pressure switch. The UV dye requires a special "black lamp" to illuminate the dye. I assume you're already aware of that if you say you're not seeing it. If you have a good pressure reading and it's showing zero pressure then you will first need to recharge the system (low side) to get the low pressure switch to energize the compressor clutch. If you can get to this point look (black lamp) for the leak. It's usually a hose going to the evaporator.

 

The dye won't help if it's leaking where you can't see it, like the evaporator which is a common failure point in the XJ, located behind the dashboard. You'd need an electronic sniffer to detect that. (Unless the leak is bad enough that you can hear it.) Those cheap low-pressure gauges built into some refrigerant cans is pretty useless. You need a real gauge set to see what's going on.

If you had some residual pressure in the system you should be OK as far as contamination from atmospheric moisture, but if it was totally empty it really needs to be drawn down with a vacuum pump. You'll also see if there's a major leak that way (it won't be able to hold vacuum).

 

I’ll have to go pick up a pressure gauge tomorrow. As for the vacuum pump, would I need to take it to a shop for that or can they be purchased?

 

First you'll want to see if there's residual pressure in the system, enough to trigger the low-pressure cutout. (Rest pressure depends on how much refrigerant you have in there and the ambient temperature. There is really no "correct" reading for this but it's typically around 70-100 psi. Maybe 20 psi is needed for the low pressure switch, I forget the exact spec.)

If all the refrigerant has leaked out you need to find the leak. If there is still a decent amount of refrigerant and the compressor is not engaging you have some kind of electrical problem.

You can also jumper the low-pressure switch and see if the compressor engages but you have to be very careful and only let it run a few seconds. The compressor is lubricated by oil carried in the refrigerant. No refrigerant, no oil, and the compressor will self-destruct pretty quickly. Then you have a major problem on your hands. You could also disconnect the compressor clutch wire, jumper the low pressure switch and check the clutch wire for 12V with a test light or voltmeter when the AC is switched on.

It is illegal to deliberately discharge refrigerant into the atmosphere, though of course if it leaked out on its own you're in the clear on that score. If you're going to be doing your own AC work you'll want to have a gauge set and a vacuum pump. Harbor Freight sells some relatively inexpensive items that are adequate for the occasional use a shadetree mechanic will give them.

https://www.harborfreight.com/ac-r13...set-62707.html

https://www.harborfreight.com/25-cfm...ump-61245.html

I have both of the above and they work fine. (Be sure to check for discount coupons!) I'm sure you can find similar items on Amazon or wherever as well. There are plenty of youtube videos showing how to use the gauge set and the pump.

 

Thank you for the help. I’ll update if I need any more advice.

 

As stated the system should have been evacuated (a vacuum pulled to remove air from system.) is there a proper amount of oil in the system ? if its been empty the system requires 8 ounces of pag 100 oil without it the compressor will not live a little low you will be okay and you will need to put in 20ounces of p134a Freon to charge the system that's 1.4 pounds. if you don't have the tools to do it correctly then your just wasting you money. I would take it someplace if you put in too much you could flood the system and the compressor will not live. The store bought cans you describe are great for a system top off when you have a small leak but not so much for a complete charge that requires special tools to do it correctly what you describe to me a low charge the low pressure switch reads pressure turns compressor on it starts to compress the Freon and pulls on the low side the pressure drops in the low side and the switch turns off the compressor then the pressure equalizes between low and high side and starts the cycle again you could add more Freon and that should tell the story the low side should read about as close to 30 psi while compressor is running but that really comes down the outside temp!

 

Just take it a step at a time and make sure no more damage is done. This stuff is not rocket science but it is a different set of tools and knowledge than what you deal with in most other wrenching. Also if you buy from Harbor Freight, I believe that their commonly-available 20% off coupon will still work with the items I linked to. (Though lately they've been adding a lot of exclusions.)

Oh, and as RockinRonnie points out if you have a major leak you need to be concerned about the amount of oil that may have leaked out. (Usually a slow leak will not lose much oil, but it will blast out with a major leak.) And also as mentioned if the system has been exposed to atmosphere the drier needs to be replaced and the system vacuumed out.

 

IS the first thing to check is the clutch is not engaging is this #10 fuse in the passenger footwell ?
Common first culprit for non-working AC ?