Attention: TDR Forum Junkies 
I thought that a fan clutch was a fan clutch. WRONG!!!!!!!!!!!! Last year going on vacation I thought my fan clutch was not working so I stop in Santa Fe NM and pick one up at autozone throw it on. The new one when its comes on is like a F-16 firing up you can really hear it and when it shuts off you can definately tell. So me thinks that the new has solved the problem. Well shortly after this the pop off on the back of the compressor started to blow off at a stop light did it a copule of times between then and the other day so I am thinking to myself just a weak popoff, air still worked ok and it was about winter so I really didn't worry about it. So now its getting warm and I want to get the air working perfect before I head back to Moab and I start to charge the thing and boom sight glass was not clear and the pop-off goes. So I check the head pressure it goes to 400psi and blows the end out of my charging hose. Me thinks this is not good. At this point I still have not figured out that its the fan. It turns it moves a little bit of air but not enough. To make a long story short THE FAN SHOULD MOVE AIR AT IDLE. I took the old clutch back to autozone along with the factory manual and explained to them what it was doing and that according to the test in the book theirs was bad they pulled out another new one and it did the same, so the guy says "Do you want your money back?" This is like a year later I said yes and he did to my surprise. The moral if the story I now have a factory fan clutch and it works! O. K. sorry to be so long winded but my wife quit listening to me so I thought I would share it here. 
