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I've been working on retrofitting my AC to R134A (the system has been sitting in a box in the trunk since I bought the car 3 years ago) for the past couple of weekends and replacing the condensor, dryer, the expansion valve and a couple of hoses...it's working -- sort of. I'm really impressed at how cold the air blows (about 37 degrees, but ambient temp was only 77 yesterday up here in Michigan) but I noticed two nagging problems.

1. The compressor squeels like crazy at idle because of belt slip. I don't know if my set up is the same as stock ford stuff (my AC unit is an aftermarket unit made by Mark IV) but the AC belt is shares a double pulley on alternator. The alternator is the only thing that can be rotated to adjust tension on the belts, by the way. The problem I'm having is that I cannot for the life of me find an AC belt that is the exact right diameter -- both belts need to be snug at the same point of pulley rotation for this to work. I've tried a 15545, 15543, 15540, 15535 and 15530 (did I mention a lot of 10 mile joints down to the parts store?). No combination matches well enough to give me a snug AC belt. That squeeling by the way -- stops when I give it the gas -- so I'm pretty sure a loose belt is the problem. Every now and then I can even see the belt stop.

2. This may be related or not. My car has what looks like a custom made idler pulley for the ac system (it mounts to the alternator bracket and sits above and to the right of the alternator. It was poorly made (who knows when) and I noticed before putting the belt on that it did not line up perfectly with the other pulleys, and in fact was somewhat at an angle. It doesn't make much if any noise, but I'm wondering what others of you with 6 cylinder engines have, if anything, for an idler pulley. NPD lists replacements for the 8 cylinder engines, but nothing for the lowly 6 bangers.

By the way, I've tried finding a belt while bypassing the idler pulley just to see if I could find one, and had no luck.

Can anyone suggest a way to determine exactly what size belts I need or can someone tell me what size belts they are using.

I don't know the size of the alternator belt I'm using but I did notice that it is narrower than the 15 series belts I've been trying thus far. Could that be part of the problem?

3. Last problem. Twice while testing the AC with various belts the compressor did not want to engage. The wire coming from the evaporator was not providing the 12 volts it needed. I jumpered a wire from the battery to the compressor and it engaged immediately. Does any one know if the part that regulates when the compressor is supposed to be activated is serviceable or replaceable?

Sorry for the long post. I've put a lot of time and money into this project and feel real frustrated. Learned a lot, and I will share the story about the plugged expansion valve later -- it was NOT a Norman Rockwell picture!

Thanks in advance for any info you can share!
 

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37 degrees sounds pretty good for an r-134a conversion.

1) Sounds like the 2 belt system with one tightening point is designed for disaster. No way will this ever work. Even if you got two belts to simultaneously tighten to the right tension, it wouldn't stay that way. Impossible design. Are you sure that the compressor doesn't have a pivot for tightening?

2) Probably linked to 1) above. The idler is probably supposed to provide a tightening function for the AC belt. You may have to modify the idler mount to get it to line up. Then, it will need a sturdy method of pivoting and putting tension on the belt via an adjusting bolt, or other positive method of locking a pivot point.

3) This may be due to pressures in the system, temperature at the evaporator, temperature setting at the control, or it could be a faulty connection or sensor.

I would contact Mark IV to discuss the 2-belt/idler problems, and they may also provide information helpful in determining why the clutch doesn't want to kick in.

Mine is a Classic Auto Air system. The big belt runs off the balancer, turning the fan and AC compressor, which pivots to tighten. The small belt runs from the compressor to turn the alternator. So, there is one pivot point for tightening each belt. They provided a new mounting bracket for the alternator to accomplish this. Can't help but think yours was intended to have a similar setup.

Good Luck! And let us know how you come out...
 

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the orig. 6cyl systems had an adjusting strap and screw to actually lift the compressor and use that to tighten the belt. it is called "compressor belt adjuster" ford part # 2A942. they cost $20 thru Classic auto air in florida. not sure if this would fit on your mounts.
 
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