So I figured out that its the tensioner that is failing - not the belts. The tensioner failed the same way it did 1 year ago - a distinct wear pattern against the hard stop. See image below. After it wears to a certain point, the spring in the tensioner fails and the belt shreds.



Here is a pic of the newly installed tensioner. As you can see, it seems the resting position of the tensioner is too close to the hard stop, which causes the wear as seen in the first picture.



So what could be causing this? I'm running an '04 5.3 block and balancer, with an '01 6.0 AC compressor and bracket. Could there be a mis-match that causes the compressor to not line up ideally? Could I space the compressor further down to increase tension on the tensioner?

Or maybe just get a shorter belt?

Any help is appreciated


Thanks for the info, I was in the process of carrying out your advice when I found the issue above.

 

I would say you need a compressor. If you watch the tensioner when the a/c is engaged you will probably see that thing bouncing all over the place. Might be able to see it with a set of gauges hooked up. I have seen this a few times.

 

I finally had some time to look at this issue again, I was out of the country for a couple weeks.

The tensioner was mounted incorrectly in my picture above, I'm a dumb ***. I fixed that and its fine now. It bounces around a little, but seems normal.

I put some gauges on, and here is what I got:

Ambient temp: 80-85 F, high humidity
AC temp: 69F
Low pressure side: 31-37 psi
High pressure side: 140-180 psi

That seems to be a clear sign of low charge. I'm going to add some refrigerant and see where I stand after that.

 

This is what my tahoe ac tensioner bounced like when the AC went south...

https://www.dropbox.com/s/eqy6hxpx1b...2019.48.57.mp4

 

that is about what mine does. how did your system fail? What did the gauges say?

 

Driving down the road on acceleration you would hear and feel a loud hard hammer/ratchet sound. Which was the ac motor binding up and causing the tensioner to ratchet/bang. Once I figured it out, I R&R'd the system. I didn't wanna wait for it to take out anything.

I never put it on the AC gauges. Just bleed the system replaced everything and then had it vacuumed and charged. No more problem. If you plan to R&R the AC, make sure you take the time to tear down the rear AC and change the expansion valve. Its not hard at all. Maybe an extra hour worth of work. You'll need to flush all the lines as well. My theory (and this could all just be a BS of a guess) is that the single compressor on the tahoe/Burbs works a hell of a lot harder thus failing more often then the trucks. I know that in the dead of summer when at idle, my tahoe ac wont cycle hardly at all if the rear AC is on (it does cycle once moving normally)

The tensioner when the ac is on doesn't move...just like when its off.

 

interesting, thanks for the feedback.

my compressor doesn't make any noise as you describe, so I hope the comp is OK.

I'm planning to do a basic re-charge first, and see what happens from there.

 

scratch that, my wife just got home with the truck and the AC won't even turn on. Maybe I'll plan for the teardown after all!

 

You cant accurately diagnose low charge by pressures only. The only guaranteed way to verify charge and the first place I start with problems like yours are to completely recover the charge then weigh in the exact factory amount then begin diagnosis.

But the pressures you stated and a cold sweating suction line means you are in the wheelhouse of where it needs to be.

 

At this point I've replaced the compressor, drier, orphus tube, rear expansion valve, all schrader valves, and the high pressure fill valve. I've also flushed all the lines, the condenser, and the rear evaporator. The only thing I have not flushed/cleaned is the front evaporator. I'm putting new seals on everything.

My next step is to evacuate the system with a pump, hold a vacuum for 2 hours, then refill.

Is 48 oz the correct amount for a 2001 suburban with rear AC? Do I need a scale to weigh the amount, or will 3x 16oz cans be accurate enough?