I have a problem with the belt staying on for the a/c on my car. My bf insists that he’s getting it on tight enough, but after a few days the squealing starts and then the belt pops back off again. Is there a reason why this might happen or is he just not getting the tension right?
Hope you guys can help…it’s friggin’ hot.
IANA Mechanic. My first guess would be that even though he may be getting the tension right, he either isn’t tightening down the bolts enough, or he forgot to put a lock washer back on. After a few days the vibration causes the bolt to loosen up and slip again.
It maybe too tight. The belt should have at least 1/2 to 1" of play, check it by pressing on the belt along its longest straight section.
Sounds like something’s not getting tightened enough or is working loose. Depending on how the belt is threaded, one or more of the pulleys will have a tensioning adjustment on it. This is often found on the alternator or some other component being driven by the belt. Also, check the bolt on the tensioner to see if there is a lockwasher of some sort present. If not, pull the bolt off and slip a lockwasher on there and re-tighten. If the bolt is oily, then remove it and use a degreaser to clean it up.
Is the entire pulley coming off or just the belt? If it’s just the belt, and the tension is correct, it maybe that the pulley’s arn’t lined up correctly. If there off just a little, that would probably be enough for the belt to work it’s way off after not to long.
Is this a new belt? If so, was it replaced because the old one came off in a similar manner, or for some other reason?
If the popping off didn’t start until after a new belt was installed, improper installation would be the most logical explanation. If an old belt started popping off, it could have been because of the belt being worn, or because of some other problem, such as a loose or misaligned pulley, a faulty belt tensioner (if applicable), a faulty or worn A/C compressor clutch bearing, or the compressor seizing up.
Well he’s convinced it’s the compressor seizing up. He said he could tell because of the burning smell and he could see something catching it. I guess he knows what he’s doing. I was hoping for something we could repair ourselves, but of course not.
Sorry, background:
We bought the car about two months ago. The a/c belt broke in about a week. The boyfriend said it looked old so he replaced that and the alternator belt. About three days after he put the new a/c belt on it did the squealy thing, smelled like burning rubber, and popped off. Repeat three times and here we are.
This really sounds like the compressor or clutch is siezing up.
I don’t know the configuration of your A/C belt, but there could also be an idler pulley seizing up. Much cheaper to fix than the A/C.
For the enlightenment of all who would ask car (mechanical) questions on this board:
The above background post contains information which is highly relevant to the situation and critical for getting anything more than general guesses about what’s going on. It’s the kind of info which, when related to your mechanic, will save him time and you money. When related to us here, it saves us time and you frustration.
(Not meaning to pick on you, Rushgeekgirl, it was just a useful example for presenting advice which I believe will be helpful to many.)
And yes, the burning rubber smell clearly indicates something on the belt’s route seizing up. Compressor, compressor clutch, and idler (if applicable) are all possibilities. If it happens to be an idler pulley acting up, that’s usually fairly easy to replace. If it’s the compressor or its clutch, special tools/equipment are generally needed, putting the repair beyond the reach of most do-it-yourselfers. With the belt off, spin the idler (if it has one) to see if there are any signs of roughness or catching.
Don’t want to raise the spectre of doom, but is there a possibility that the OP’s vehicle was originally R12 and a less than complete cleaning of the system was done in converting to R134a which is causing the A/C compressor to resist turning?
Ah that’s okay. I’m only asking out of curiosity. I am leaving all the work to him and his mechanic. I dashed off the post this morning after it popped off wondering if anyone knew …I should have given more information then and mentioned that he was handling it. I just have those silly trust issues! 
In that case you would hear the a/c clutch engage and disengage continuously.
No. That sort of rapid cycling is typical with a low charge of refrigerant that has enougn rest pressure to trigger clutch engagement but then operating pressure so low that it triggers disengagement. A compressor that turns stiffly or is seized would not have that symptom.
He tried that this morning and there was a catch so he replaced the pulley. We did some errands this morning and there’s still a slight squealing sound but maybe he still doesn’t have the tension right. It’s not catching anymore, so that’s good I suppose.
He’s determined to fix this himself. He was supposed to take it in this morning, but I think it was killing his manhood.