How do I test the AC clutch?

So this new "to me" 01 XJ is the newest Jeep I've ever owned. I've already discovered the dreaded 0331 head is there (crossing fingers its not cracked) and have just begun to see what this thing needs. The PO told me the AC blows but only cool... So thinking it may just need a recharge I got to looking at it today. Well... the first thing I noticed is that the clutch on the compressor isn't engaging when its turned on? I opened the fuse box under the hood to check the AC fuse and it looks ok. Both the big (30 or 40 amp IIRC) and the little tiny one both seem fine. I know there is another panel inside on the passenger side but I have no idea which fuse is which. *What ever happened to printing it on the cover?* And since all my old Jeeps only used one wire to go from the compressor which acted as a ground... why does this one have two? And while I can freely spin the clutch.. how do I make it lock up and what should I check? Any help would be awesome! Thanks all!

There is a pressure switch on the system. If the charge gets low, the clutch won't be activated.

Add freon/oil to the system and it should start coming on. 30 PSI is what it should be filled to for it to run properly but pulling a vacuum on it at a shop will find a leak if there is any.

Disconnect the clutch wires, and apply 12 volts with a jumper wire set from the battery and see if the clutch engages first. IF it does, get a set of AC gauges, about $40 on sale at Harbur freight, and check the pressure. It should have about 80-90 PSI when off (not running), on both sides, high and low.

Alright! Thanks everybody!!! I pulled the wires and grounded them to the bat and the clutch kicked in. Grabbed one of those all in one freon recharge bottles and hooked it up to the low pressure side. Ran the Jeep for a bit and added the entire can. At first it did nothing.. then it slowly began to cycle the clutch. Once the can was about empty it had gotten to where the clutch stayed engaged. I'm not sure if that one can was enough but at least I now know it functions. Cold air is a blowin' and I'm all giddy! Nothing ever works out so easy for me. Haha! I'll keep tabs on it and see if it gives me any issues. If it does and I can't find a leak I will take it to someone that understands more about AC than me, which is pretty easy.
Now on to figuring out if the head is cracked or not...

Might want to pay a local shop to do a sniff-leaf test while it is running, find any leaks the easy way now.

^^Exactly, the refrigerant had to go somewhere... A dye can be added to the system and leaks found.

o-gauge-steamer said:

^^Exactly, the refrigerant had to go somewhere... A dye can be added to the system and leaks found.

Click to expand...

I found the dye to be useless for finding front shaft seal leaks.....The electronic detectors are far more sensitive and found leaks that the dye missed on several of mine.