This 2003 Chrysler Town & Country Mini Van came in with the complaint that sometimes the air conditioning is not cold and sometimes it works fine. Seeing as how refrigerant charge normally will not cause this condition, I decided to run the vehicle with the a/c on and the controls set to full cold and low blower. This will force the compressor to be cycled on and off. I set the parking brake, chocked the wheel and left it running while I listened to the a/c clutch cycling. After about 20 minutes of cycling I could not hear any more changes. I went to investigate and sure enough the clutch was not turning. Being down this road before I looked at the odometer reading and it was 180,000 +. With that in mind I accessed the compressor clutch hub and pushed it in with an old broom handle, the clutch engaged and worked fine until it was time to cycle off again. It cycled off and would not come back on until I hit it with the broom handle.By the way I do not recommend my method to the average person as it can be dangerous. The preferred method is to access the a/c compressor and measure the clutch gap with a feeler gauge and compare it to the manufacturers specifications. Be sure to measure in at least three locations for an average reading.
The gap on this clutch was sitting at about .060″ and should have been around .015″ to .020″. The next step was to remove the center bolt. Most of the time you can hold the clutch hub with your hand and then use a ratchet and socket to remove the bolt.
Sometimes you will need a tool similar to the one shown below which is specifically made to hold compressor clutches. After the bolt is removed you will need to grab the hub ring and pull it off while slightly rocking the hub back and forth. DO NOT PRY ON THE CLUTCH HUB AS DAMAGE MAY OCCUR.
With the clutch hub removed you now need to remove all of the shims. Because of magnetism you will probably have to push them through from the front and garb them at the rear of the hub.
Calculate the amount of shims needed to be removed by subtracting the manufacturers specifications from the readings you took earlier. You may have to go to a parts store for a shim assortment to be able to properly shim the clutch to the right specs.
This is becoming a regular repair on a lot of vehicles because the vehicles and compressors are lasting longer than the clutch is designed to. My experience is that if the compressor sounds and tests good at the time of adjustment the owner can usually get another couple of years of use before something else goes wrong with the system.