Altenator/Ac comp/Fan belt keeps loosening problem?

I am willing to bet you have a housing erosion problem... Probably under the alternator... That bolt that is underneath it has a problem (at least on one I bought) of working loose no matter how tight you get it and will vibrate and chisle away at your metal on the housing under the alternator.. It is either going to be that the tension arm over the alternator or you have a bad pully somewhere.. The only other thing it might be is user error..

Here is what I would do pull the alternator off check the bolt housing and make sure your tension arm isn't worn or broke also make sure you have tightened up the tension arm on both sides of the bolt and the arm (I know it is common sense but you would be suprised and what we all over look) If the bolt housing is worn or looks like it has been eaten at get a bunch of washers and shim it up it will last forever this way.. If your tension arm is worn or cracked get a new one they are 40 bucks at freightliner. While you have it down play with your pullies makesure they don't wobble to much all pullies will have a bit of give in them but they shouldn't be a loose wobble it should be a tightish type feel.. If you have a bad pully you will be able to tell.. The only other thing I can think of is the arms the pullies attach to may be cracked...

And I just reread your post too.. also pull your ac compressor down.. (don't break lines) and check the compressor housings on the compressor and the mounting housing to make sure it isn't worn down.. Good luck. Nothing like hunting for an animal you don't know..

 

I'm lazy, so I would measure the belts now, and then again the next time they come loose, to see if that's the problem. Maybe you just got a couple of defective belts.
Then I would proceed with the above advice.

 

Make sure and use good quality name brand belts too, they are NOT all the same. I had a recurring problem like yours with kelly springfield belts from auto zone, they are complete crap. Put on gates the third time, and it never happened again.

 

Check alignment of your pulleys, and make sure they are all in line, since over time all these brackets and mount holes wear and can cause miss-alingnment. You also need to check for pulley wear, because if they get worn out and badly curved in the middle of the groove, from slipping, you'll never keep belts from wearing out quickly no matter how tight they are. The will tend to slip under load on an alternator, right after start up (that's when you'll hear them squealing from slipping). Also make sure that there is no oil or water getting on them casue that plays havoc with them too.

 

Sometimes the "V" of the pulleys are just too worn and grooved out. The angle of the belt doesn't match the angle of the V anymore and so the belt quickly gets worn and cut down or bottoms out and doesn't even grab in the V enough.