AC Compressor and belt tension question

Topic: AC Compressor and belt tension question (Read 1498 times) previous topic - next topic

AC Compressor and belt tension question

March 29, 2013, 09:37:40 pm

This compressor and belt were replaced in August last year. Now when I turn on the dash AC and the compressor clutch engages, the belt squeals and the compressor pump spins haltingly.
Question is; do I have a problem with the compressor or a loose belt? I suspect the belt as I can depress it about 1 1/2".
How tight should it be and how do I tighten it? How much depression, 1/2", 1", ??
The pump is attached with 4 bolts. In the attached photo, the idle pulley does not seem to be a spring tensioner (at least I can't budge it). I'm thinking I should loosen the 19 mm bolt indicted in photo, pry that pulley back to increase the tension. Is that correct?
How can I get enough pressure on it to tighten it enough?
Any ideas appreciated.
Since the vacuum generator has been inop, I haven't tried this in a couple months and before that we were in Oregon (no need there). Today I tried it just as we were checking into a park, window open talking to security guy. Heard squeal and shut it off right away. Luck of the Irish me thinks; belt looks fine.
Thanks.

Re: AC Compressor and belt tension question

Reply #1 – March 29, 2013, 10:41:22 pm

If you grab the belt half way between the compressor and the drive pulley, you should be able with a bit of difficulty, turn the belt 90 degrees with your fingers. A belt with the play yours has will slip more and more, will produce heat doing it, will glaze the belt surface and stretch even more. I have a Detroit so the adjustment is different. Perhaps another member can give you the tightening sequence to get it done just right. Before you just tighten it, check the condition. Small cracks may be seen towards the bottom of the "V" in old or damaged belts. Glazed, hardened belts are another reason to renew at inspection time. ALWAYS replace belts in pairs if you have two. If you replace belts, check them frequently for the first several thousand miles.

I have seen others tighten the belts with a big lever until the belts are too tight. This is the number one cause of alternator bearing failure.

Pierce

Re: AC Compressor and belt tension question

Reply #2 – March 29, 2013, 11:30:19 pm

Dick, the 19mm bolt needs to be loosened, which is a bear to do because of the position that it is in. After you get it loose you need a extra pair of hands with a pry bar to increase the tension on the belt. Belt deflection should be about 1/2".

I built a bracket that bolts to the engine gear housing cover and a turnbuckle setup that allows me to do all this adjusting by myself. I am going to try to upload a couple pictures of my setup.

Re: AC Compressor and belt tension question

Reply #3 – March 30, 2013, 12:43:30 am

And the special tool was born. Nice!

Pierce

Re: AC Compressor and belt tension question

Reply #4 – March 30, 2013, 05:43:20 am

I just looked at the pictures and the location of the tensioner pulley just seems so wrong!! The more the tensioner pulley is moved out the less "wrap" on the drive and driven pulleys.
Seems almost as if the adjustment is self-defeating from an engineering standpoint. The more tension put on the belt to stop the squealling the more force put on the bearings and the belt itself.
Wouldn't a belt pulley that runs on the outside of the belt work better?? More wrap created with less tension.

Re: AC Compressor and belt tension question

Reply #5 – March 30, 2013, 06:28:09 am

Quote from: nitehawk – March 30, 2013, 05:43:20 am

I just looked at the pictures and the location of the tensioner pulley just seems so wrong!! The more the tensioner pulley is moved out the less "wrap" on the drive and driven pulleys.
Seems almost as if the adjustment is self-defeating from an engineering standpoint. The more tension put on the belt to stop the squealling the more force put on the bearings and the belt itself.
Wouldn't a belt pulley that runs on the outside of the belt work better?? More wrap created with less tension.

nitehawk, Bingo, total agree, if mine was like that it would have been changed already,
Good catch, like your thinking
Dave M

Re: AC Compressor and belt tension question

Reply #6 – March 30, 2013, 07:48:39 am

I noticed the position of the idler pulley, too, and then saw the other comments. I don't think that kind of belt is supposed to bend backwards but since it's a manual tension adjustment I'd think it would be on the other side so the wrap on the big pulley would be more.

Re: AC Compressor and belt tension question

Reply #7 – March 30, 2013, 08:10:56 am

I will have to look close at mine 8.3 Cummins but I BELIEVE that the AC compressor does not have an idler pulley, it simply is pushed outward with a bolt after the locking bolts are loosened. I don't like the looks of the idler set up but each of these rigs is different.
Gary B

Re: AC Compressor and belt tension question

Reply #8 – March 30, 2013, 08:15:45 am

Dick, the belt tension is a vital factor in obtaining maximum operating efficiency and belt life. V-belt drives must be under proper tension during operation to produce the wedging action in the sheave grooves that give them their pulling power.If belt tension is too low, there will be slippage and rapid wear of both belts and sheave grooves, which will be apparent by the squealing noise. Correction of slippage should not be attempted by application of belt dressings. These usually contain chemicals that tend to soften V-belts. Although immediate improvement or slippage reduction may be accomplished, eventually deterioration of the rubber compounds will shorten belt life.

The tensioning may be accomplished by tightening until the proper feel is attained. The proper feel can be described as a lively springy action of the belt. A way to check this is to strike the belt with the hand. They will feel alive and springy if properly tightened. If there is insufficient tension, the belt will feel loose or dead when struck. Too much tension will cause the belts to feel taut, as there will be no give to them.

The preceding was a quote from the Maintenance guidebook on belt tensioning. I agree with Ronb with the 1/2" deflection assessment. For the length of belt it should be a good starting point. There are specific tools and calculations which are available to give a more precise deflection guide, but by using common sense you should be able to get rid of the squealing. I hope that it is noted about the belt dressing applications. Many people think that they are a godsend, but they definitely cause much more long term harm than good.

Hope you can use any of this info.

Larry

Re: AC Compressor and belt tension question

Reply #9 – March 30, 2013, 08:20:22 am

nitehawk,
I have to agree with you. The more tension placed on the belt the greater the reduction in grab on the pulley. I believe it could have a better design. A tensioner pulley designed for the back side of the pulley would make much more sense.

Re: AC Compressor and belt tension question

Reply #10 – March 30, 2013, 11:27:49 am

After my earlier post, I realized my setup is identical to Dick S's setup? So I decided to get into this V-Belt issue, while I like the idea of more wrap on both drive & driven pulleys I feel running the idler on the back side of the belt must be a design issue unlike the multi groove flat belts. So I went to my local truch / auto parts house, they have never seen a OEM setup with idler on the back side of a v-belt, so I just replaced my a/c belt Gates 9440 was a snug fit. Tensioning was very simple, the more difficult was the bolt to secure the positioning, did require 3, 3/4" combination wernches due to lack of pace could onl get a very small turn, each different werenh had different position of the 12 pt. A SnapOn fine tooth ratchet would be the simple answer, mine is the course tooth. So it is done, getting good tension is easy Amen
FWIW
Dave M

Re: AC Compressor and belt tension question

Reply #11 – March 30, 2013, 11:45:29 am

Dave,

Have also never seen a V belt with a backside tensioner. Probably not stable enough and might cause the belt to flip almost 120 degrees on it's side.

Pierce

Re: AC Compressor and belt tension question

Reply #12 – March 30, 2013, 12:45:30 pm

The belt drive for the grass/leaf bagger on my John Deere tractor has flat pulley tensioners that support the back side of a v-belt. It is definitely a kludged up system, but it does work. The belt traverses several turns and twists.

Re: AC Compressor and belt tension question

Reply #13 – March 30, 2013, 12:59:56 pm

Jd, it is mazing what can be created with little red neck engineering, where low cost is the major concern. A proper engineered unit costs a lot more and has a much longer life
.

Re: AC Compressor and belt tension question

Reply #14 – March 30, 2013, 01:42:19 pm

What are called flat belt flanged idler pulleys are used on the backside of conventional V belt.Gam

Re: AC Compressor and belt tension question

Reply #15 – March 30, 2013, 01:52:57 pm

"Flat Idler Pulley"
Like JD, I have a backside idler on a V belt on my mower. Looks just like this:
http://www.surpluscenter.com/item.asp?catname=powerTrans&qty=1&item=1-3900
BTW this is a fun catalog to look through for the tinkering type. They save some real deals in here IF it something you can really use. (I have no affiliation with them)

Re: AC Compressor and belt tension question

Reply #16 – March 30, 2013, 02:23:16 pm

They used to be called Burden's Surplus Center because Jim Burden and his dad owned it. The dad died years ago, and Jim would be in his 90's if he is still living. I went to church with them and one of their daughters was confirmed with me. I wonder their son is now running it, or maybe his son, since their son is a few years older than me. The store had lots of new stuff as well as military surplus stuff. Neat place to just wander around for a few hours.

Re: AC Compressor and belt tension question

Reply #17 – March 30, 2013, 03:20:43 pm

Lawnmower quality is not accepted on my Foretravel. It might work fine, you can experiment for the rest. of us.
Dave M

Re: AC Compressor and belt tension question

Reply #18 – March 30, 2013, 03:31:57 pm

I must admit that the reason I caught the odd pulley location was because of the belly drive on my tractor for the two stage snowblower. I had initially put the tensioner pulley on the wrong side (using the theory that it was a v-belt and should not be bent backwards) and the belt squealed and stopped driving the snowblower whenever I put a load on it. I moved the pulley to tension the outside of the belt and It feels like I could throw ice chunks. No slippage. The tensioner pulley IS flat-bottomed. So, I think a little deflection would not be detrimental.

Re: AC Compressor and belt tension question

Reply #19 – March 30, 2013, 05:45:51 pm

OK, OK, have seen something new to me here. I can see a real advantage to pushing the belt back in as it would increase the amount of contact area on the pulleys on both sides. Especially if you used a longer belt and brought the tensioner inside the centerline. Bound to be able to transfer more power without slipping with a greater contact percentage of the pulley circumference.

Pierce

Re: AC Compressor and belt tension question

Reply #20 – March 30, 2013, 05:59:38 pm

Quote from: Dave M – March 30, 2013, 03:20:43 pm

Lawnmower quality is not accepted on my Foretravel. It might work fine, you can experiment for the rest. of us.
Dave M

Quote from: Dave M – March 30, 2013, 12:59:56 pm

Jd, it is mazing what can be created with little red neck engineering, where low cost is the major concern. A proper engineered unit costs a lot more and has a much longer life.

Quote from: Dave M – March 30, 2013, 11:27:49 am

..................So I went to my local truch / auto parts house, they have never seen a OEM setup with idler on the back side of a v-belt, so I just replaced my a/c belt Gates 9440 was a snug fit.............................So it is done, getting good tension is easy Amen
FWIW
Dave M

Sorry Dave,
You are in error. There are thousands of hours on thousands of these machines, in commercial applications and they use V-Belt Flat Back Tensioners in Fixed and Torsion Spring loaded applications, with MUCH higher torque loading than the FT/Cummins AC compressor applications.
My JD was built in 2000, has over 3000 hours on it, and has had one new serpentine V-Belt for the 72" mower deck. And that one belt was needed because of a gear drive mounting bolt failure (which subsequently damaged the belt). Not because the belt was worn out.

Lastec 100" Deck Engineered for John Deere 1565

Conversely, I've had many belts and two sets of tensioners on my FT.

They (JD) may be red necks and experimenters, but their belts don't squeal and carry on like my "engineered" FT/Cummins 8 ribbed Alternator drive belt and associated tensioners. FT and Cummins were not able to solve the squealing in 12 years of trying and then subsequently tried to re-engineer my solution in the backward direction. My AC belt didn't squeal, by the way. Just the Water Pump/Alternator belt.
As I posted earlier, I finally solved it myself, through no help from them.

Just saying, don't cry MRCI (Myopia due to Rectal Cranial Inversion) when the Red Necks are winning! They may throw it back at ya!

Because its hard to see in the U-Tube Clip, I've attached a couple of documents that show my/JDeere serpentine configuration.
Neal

Re: AC Compressor and belt tension question

Reply #21 – March 30, 2013, 06:34:18 pm

Hi Neal,
Gosh I do wish that I was a word smith too, however I am not. Yes one can add all sorts of issues to the discussion, but bringing in the serpentine design just takes up words but adds nothing to the V-Best discussion.
I am amazed that all this still goes to the lawn mower designs, and I do agree there are some interesting V-Belt configerations used on the mowers that have worked for mowing grass.
Maybe an example being used on a sucessful upper end highway design using the idler in the back of a V-Belt. With your vast experience and knowledge, I am sure you have a few working examples.
Yes, I do love the red neck engineering, Have seen it makes fools out of the highly educated wannabees that were out of their tree.
I have been wrong before.

With Respect
Dave M

Re: AC Compressor and belt tension question

Reply #22 – March 30, 2013, 07:00:50 pm

For those of you not able to fix the Cummins "squeal" this could be a blessing in disguise and a hint to re-power with a 2 cycle Detroit.

Pierce

Re: AC Compressor and belt tension question

Reply #23 – March 30, 2013, 07:09:00 pm

Pierce,
I love it, and I wonder if your DDC has the V-Belt driven alternater or a direct gear drive setup, both are good, problem with the gear drive, when it screws up, it can get costly.
Dave M

Re: AC Compressor and belt tension question

Reply #24 – March 30, 2013, 07:37:00 pm

No, our alternator is up top with a couple of belts with conventional method of taking up the slack. You do have to bend over the bed sides and risk a stroke to change them. A Leece-Neville 190 amp as I remember.

My old 4107 had the brushless, direct internal drive 300 amp alternator. It was engine oil cooled so had a 100% duty cycle and could charge flat batteries forever. I can imagine if anything went wrong with the gears, it could be expensive. In fact, there were no pulleys of any kind on that engine. The big fan was driven by a PTO and the AC compressor came off that also with a tiny U joint I think. Nothing else rotating on the outside of the engine.

Pierce

Affiliate Notice