Air conditioner belt shredded

[72ray]

Just shredded the a/c belt! 1972 350 auto with ps. A/C was on and we were on the freeway traveling at around 80 mph when it all of a sudden the belt started to slip (squeal) and emit smoke. Turned off a/c and it’s clutch kicked in stopping the mayhem. Not sure why it happened. Suspicious that the compressor has seized.
Now, how to fault test and diagnose. Any tips? TIA

 

[72ray]

Just shredded the a/c belt! 1972 350 auto with ps. A/C was on and we were on the freeway traveling at around 80 mph when it all of a sudden the belt started to slip (squeal) and emit smoke. Turned off a/c and it’s clutch kicked in stopping the mayhem. Not sure why it happened. Suspicious that the compressor has seized.
Now, how to fault test and diagnose. Any tips? TIA

The compressor is less than a year old

 

[ddgermann]

The compressor is less than a year old ☹

How long is a piece of string?
Could be a few things. Assuming it was working and delivering cold air...
- Is the compressor factory or an added aftermarket?
- Wrong refrigerant with no lube properties?
- Just old and wore out (bearings finally piled up)

On the bright side it’s an easy repair although not cheap to replace and recharge.

 

[XFIRE82]

grab the pulley ( no belt on ) and see if you can turn it , if not then the clutch bearing seized ( but I doubt that ) . Then grab the clutch hub itself and see if can turn the compressor , if not then the compressor is seized. If oil was not added to the system with the freon then lack of lube and she will seize up. Also a plugged expansion valve can stop the circulation of freon causing very high pressure and can bust the compressor .

 

[72ray]

Thanks. Plugged expansion valve is an interest suggestion. I guess the evidence of that would have soon disappeared as it thawed out. It’s an 8 month old compressor with lube added when charged. Free spooling atm with a sad belt still in place ie clutch appears to be good. Got a fresh belt today. I’ll see if I can figure out how to disengage the clutch and turn the compressor with the engine off.

 

[XFIRE82]

the clutch is only engaged when power is applied to it , otherwise you should be able to turn it. If you can't turn it with power off then there is a problem. Plugged exp valve is usually a tiny piece of debris that plugs the hole, could be a piece of rubber from the hose or some foreign object during installation.

 

[ddgermann]

the clutch is only engaged when power is applied to it , otherwise you should be able to turn it. If you can't turn it with power off then there is a problem. Plugged exp valve is usually a tiny piece of debris that plugs the hole, could be a piece of rubber from the hose or some foreign object during installation.

Excellent advice Michael

 

[72ray]

Got onto it today and yes the compressor turns. Good news! Think I’ll fit a fresh belt And book it in to have the ac system checked over when they have time. I’ll post any progress/ findings here. Thanks all.
I’m guessing this belt changing fun is why folks retrofit with serpentine belts

 

[XFIRE82]

it could also be that the belt was not very tight to begin with. You were going 80 , so she was turning pretty good and when the compressor kicked in then the belt could not grip enough at that rpm , slipped as trying to pump , started smoking and finally blew the belt. But good to hear the compressor is not toast.

 

[72ray]

On that point how firm are you guys tightening the various belts. I was always told that ‘over torquing’ alternator belts shortened the life of the alternator bearings. AC belts appear to need a good tight belt as referred to above.
Meanwhile how about the power steering belt? I’m finding it a challenge to get any good torque on it. What’s a good technique or do you build a special tool?

 

[XFIRE82]

It is important to use a good quality belt like Gates or original GM . Some jobber ones like Napa stuff like to stretch easily and are no good, even Dayco top cog don't work well . Especially on the A/C you need a good strong belt that don't stretch . I just tighten them so that the belt does not whip while running . You can see it just by revving it up and watch how the belt runs. When the a/c clutch kicks in you can really see the load on it and if lose it will whip , so try tighten it to get as much slack out of it as possible. Yes, if overtight then it puts pressure on the bearings and can shorten the lifespan. The ps pump does not need to be very tight as it is a big pulley so it has alot of grip surface. The alt is a small pulley so needs to be snug as to not slip while charging a heavy load, same thing watch so it does not whip revved up but it does not need to be fiddle string tight either. So just get good quality belts like Gates or GM and they won't stretch causing problems.