A/C belt tensioner chattering
 

While on a short road trip last week the A/C belt tensioner started chattering, drove it that way all day got home and the next day I looked at the A/C belt and it was shot all weather cracked and worn. I have 114k miles on this thing so I installed a new serpentine belt and the a/c belt. The tensioner does not chatter like it did but you can hear it some times. I am hoping that its just the tensioner that's gone bad due to the bad belt and I can get away with just changing the tensioner. The other thing that worries me is that when we turn on the A/C the vehicle runs a little rough leading me to believe the compressor may be going bad and causing the chatter.... has anyone gotten away with just changing a tensioner and fixing this?

Anybody??

welcome to the forum,
What year is the vehicle?
the pulley most likely needs to be replaced,as for the poor idle when the AC is on the throttle body and throttle plate probably need to be cleaned of carbon build up...

Its a 2001 Suburban 1500 with a 5.3L Thanks. Yes I already cleaned the carbon because the throttle was sticking a little in the closed position i cleaned it as best as possible Including the throttle plate but I did not take the throttle plate off

Tensioner is not an uncommon failure. Easy to replace, but you have to get under the truck to replace it. 2 bolts and you are home free.

Yea I changed the tensioner and its still chattering I guess I'm changing a compressor next

I had an '01 Silverado 2500HD with the 8.1L and Alison 5 spd trans. My truck did the same thing and I replaced the tensioner as well turned out the clutch was going out in the A/C. Just make sure that if you are planning cleaning your throttle body that you take it off the truck to do so. I was cautioned by my local dealer mechanics that if the cleaner gets into the combustion chamber that it will react with the O2 sensors and the Catalitic converters.

while I was under the Suburban i turned the compressor and there was a steady resistance the clutch felt fine so I am ordering a compressor tonight (ouch) On the throttle body I just sprayed carb cleaner on a rag and wiped the inside of the throttle body till it was clean. I did not want that crud running into the cylinders.

keep in mind replacing the compressor is not always necessary the clutch assembly can be replaced if that is the cause of the chatter. replacing the clutch if its possible for the compressor you have will save you the trouble of opening the system

the chatter its coming from the belt tensioner bouncing up and down I can duplicate it by reving the eng a little while staring at the tensioner. how would the clutch cause this? could it be engaging and disengaging rapidly? the higher I turn the a/c up the worse it gets.

have you checked the charge on the AC? rapid cycling could be a sign of over or under charging of the system...

How can you tell the noise is coming from the tensioner and not a compressor bearing? The tensioner will move when the load (A/C compressor) is engaged and released.

The noise is coming from the tensioner bouncing up and down, it only happens when you are accelerating.

In your previous message you stated you were ordering a compressor..
I suggested that a worn clutch could possibly cause the chatter, and on some compressors the clutch can be replaced without replacing the whole compressor unit.
But it looks like you have identified the tensioner as the cause..
A rapid cycling clutch can be a sign that the AC system needs to be charged...

in2pro, I got to the point were money wise I do not want to put a compressor in after all the reading about this problem. I am going to take it to the dealer tomorrow morning and for the $89 and let them diagnose it. if it needs a new clutch I will just let them do it. anything more I am going to have to do it myself. This thing has been dealer maintained its whole life up until about 50,000 miles ago but who can afford that anymore.

Basically the system is working fine, its not cycling rapidly, the compressor is not making any bad noises, the air in the car is nice and cold. after the belt tensioner started chattering I replaced the belt and put a new tensioner in and now it is still chattering when I turn on the A/C and you are applying throttle. my last theory is maybe the clutch pulley is worn to the point that the new belt is slipping under acceleration.

Ah I understand now... when you say you replaced the tensioner did you replace the tensioner arm and pulley or just the pulley....
reason I ask is typically they pulley only is replaced (because the bearing goes bad) not the entire arm....
but I would be suspicious of the arm itself as it would seem that they too would get weak over time and not apply the needed tension...

Please let us know what the dealer finds and thanks for the patients:):)

I replaced the whole assembly took 10 minutes. one of the stops actually broke off on the old one from the chattering and the pulley wheel was well worn. I'll let you know tomorrow what the dealer $ays

Yup Its the compressor...... so now I'm going to change it and I read that you have to flush the system and change the accumulator and the orifice tube.

The dealer wanted over 1k bucks to do the job

dang sorry to hear that and thanks for the follow up...
are you able to do the AC repairs yourself? its the evac, flushing and refilling that make it hard for the lay person to repair AC systems because of the equipment needed....

If you have an empty freon bottle, you can save most of what's in the system by setting it in ice water and connecting it to your system (not running). At $10-$15 a 14oz can, it's worth the extra effort.

You'll need a set of gauges and vacuum pump. Both are reasonable at Harbor Freight.

If they still put desiccant in them, you'll need to replace it. Used to be in the accumulator but not sure on the R134a systems. Someone else may know.

Well I got everything in myself(compressor and accumulator) took it to the shop where they put a vacuum on the system to remove moister and check for leaks then add freon, it all came out to a little over $500 bucks. That's half of what it would have cost to have it done. Thanks for the help

that's good to hear wish they could have cut you a better deal as that sounds a bit pricey but at least its done!

That price included all the parts also and o-rings and seals for the whole system