Noises - Alternator, A/C Compressor

MedicPatriot · **Posted:** Mon May 13, 2013 1:46 am

There has probably been some noise coming from my serpentine belt system (somewhere) for a year. When I had my engine worked on the mechanic noticed this and said there were two noises. He said one seems to be coming from the alternator, and the other from the A/C compressor (it gets loud when you turn on the A/C but it works. This has been going on since last summer. I actually have had a few dead batteries this winter, but I attributed it to the old battery (came with the car), and the mechanic said my alternator is charging the battery.

I opted to not have this fixed yet. I already had enough money to spend on repairs. This won't cause any "harm" right? I am pretty sure the worst that would happen is my alternator would cut out and I would be stranded, but nothing extra could get damaged.

He says it might go up eventually, but I swear this noise has been these for quite a long time with no issues.

DOC4444 · **Posted:** Mon May 13, 2013 7:16 am

If you have red dust on and around the alternator, it is time to get a rebuilt from Advance, etc. The clutch will seize and throw off your SB.

DOC

papaindigo · **Posted:** Mon May 13, 2013 8:07 am

Crank up; open the hood; may have to remove engine cover; look down serp belt to the tensioner (lower passenger side); if tensioner is bouncing around (not just minor twitching) immediately stop engine and do what Doc says. Do not let local shop rebuild alternator unless they also install a new OEM equivalent alternator clutch pulley, anything less will either fail early and/or take out your tensioner.

If you have over 50K miles on original serp belt it's probably time for a new serp belt.

MedicPatriot · **Posted:** Mon May 13, 2013 5:18 pm

Hm. No red dust or anything.

The noise is not that bad when idling. It sounds like a chirp. The belt/tensioner did not seem to be moving to me.

When you turn on the A/C it becomes fairly loud. Then you can see the serp/ belt bouncing around pretty good.

CATCRD · **Posted:** Mon May 13, 2013 10:46 pm

MedicPatriot wrote:

When you turn on the A/C it becomes fairly loud. Then you can see the serp/ belt bouncing around pretty good.

Yep, that's a bad clutch. Make the same observations while a helper holds it stopped in drive. If the tensioner is bouncing like a blur then the clutch is bad.

MedicPatriot · **Posted:** Wed May 15, 2013 1:15 am

Actually it sounds really terrible when the a/c is engaged. The belt bounces.

Question: would the a/c compressor cause noise with the a/c off, or is the other noise from somewhere else?

papaindigo · **Posted:** Wed May 15, 2013 9:34 am

When the AC clutch is disengaged (e.g. the AC is off, keep in mind the AC runs when the interior AC/heater vent switch is in certain positions even if AC is not "turned on", or when it's on but the compressor is not cycled on) the compressor should be quiet. The most common cause of belt/belt tensioner bounce is a bad alternator pulley. I don't know if the AC compressor or compressor clutch can cause similar bounce but I do know the AC compressor is much more expensive to replace and likely not DIY than the alternator.

Your options on alternator replacement are OEM, a bit pricey, Autozone Duralast 15457 or AdvanceAutoParts PN 12668 which likely are special order and cost ca. $145, or just replace the alternator pulley Mopar53013554AE or Litens 920720 which cost about $85 but may be difficult to remove without the special tool (some report luck using an impact wrench with an appropriate allen key) although no special tool is needed to reinstall.

Offhand my suggestion is to simply replace the alternator and see if the problem goes away. However, the bottom line is if the belt is bouncing you need to identify and fix the problem or that bounce will shortly take out the belt tensioner which costs more $s

flash7210 · **Posted:** Wed May 15, 2013 11:22 am

MedicPatriot wrote:

Actually it sounds really terrible when the a/c is engaged. The belt bounces.

Question: would the a/c compressor cause noise with the a/c off, or is the other noise from somewhere else?

Sounds like a bad bearing on the AC compressor clutch.
Usually the AC clutch/bearing assembly can be serviced separate from the compressor,
assuming that the bearing didn't tear up the shaft or housing.

CATCRD · **Posted:** Wed May 15, 2013 9:56 pm

MedicPatriot wrote:

Actually it sounds really terrible when the a/c is engaged. The belt bounces.

Question: would the a/c compressor cause noise with the a/c off, or is the other noise from somewhere else?

There is more engine load when the AC is engaged, stronger power pulses from the pistons, and therefore more belt jump. Same effect as when you hold it stopped in gear. What was the result of that test?
Does the jumping go away when you bring the engine speed up to 1500 or 2000 rpm?
All signs still point to a bad alternator clutch.

MedicPatriot · **Posted:** Sat May 18, 2013 8:34 pm

Ok so I had someone hold it in drive.

Normally it sometimes makes a slight chirping sound but I can't notice anything moving.

When in gear It does chirp slightly more then when in park. Still, I can not see movement.

When you engage the A/C it makes a hideous chirping noise and the belt bounces. To me it seemed like just the belt was moving, I couldn't tell if the tensioner was. When you rev up the RPM's to 1500 the sound goes away entirely. The sound is only there when at idling engine speeds.

So my question is...is this the A/C compressor, alternator, or both? I just can't see how it would be the alternator if the sound is mainly only there when the A/C is engaged. I don't see how replacing the alternator would fix this, but I would like to learn from the knowledge on this board.

Thanks.

DOC4444 · **Posted:** Sat May 18, 2013 8:46 pm

I lean towards agreeing with CAT because 99 times out of 100 it is the decoupler, but the reported lack of the tell tale red dust on the alternator makes me unable to rule out an AC clutch problem. I am not aware of anyone having an alternator decoupler failing without exhibiting red dust.

Anyone?

DOC

MedicPatriot · **Posted:** Sat May 18, 2013 9:12 pm

I was looking at it and thought there might actually be some red dust on there. If it is, it is a very dark red. Maybe I will try to snap a picture tomorrow.

I still don't understand how the alternator would cause noise when the A/C is on. Are you saying that it could be only the alternator?

DOC4444 · **Posted:** Sat May 18, 2013 9:27 pm

Yes, the dust is very dark red. Finally, this all makes sense! And yes, get a rebuilt alternator from a place like Advance. Easy, quick and inexpensive to replace. It costs half as much for the parts to replace just the decoupler, but the job is often gnarly, even with the VM tools of which I have a full set. (I chose to replace alternator.) Trust CAT.

DOC

MedicPatriot · **Posted:** Sat May 18, 2013 9:34 pm

I will replace the alternator ASAP.

Still my question remains, how could noise the only happens when the A/C is on be related to the alternator? I really do not get this.

CATCRD · **Posted:** Sun May 19, 2013 2:56 am

MedicPatriot wrote:

I will replace the alternator ASAP.

Still my question remains, how could noise the only happens when the A/C is on be related to the alternator? I really do not get this.

If this noise has been going on for over a year we can't rule out that some damage was done to the AC clutch by the excessive belt jump caused when the alternator clutch goes bad. The noise actually comes from the belt slipping on a pulley. It depends on things like the strength and frequency of the power pulses from the pistons, elasticity of the belt, and inertia of the rotating components on the accessory drive. When you turn on the AC it puts your accessory drive into the sweet spot for this resonance. When you rev it up you take it out of the resonance zone.
There is a test you can do for the alternator pulley. With the belt removed you can hold the alternator shaft still with a wrench. I believe there is a place to do this at the back of the alternator. I'm not near my jeep right nor so I'm going from memory. With the shaft held still you should not be able to turn the alt pulley clockwise, but you should be able to turn it counterclockwise with minimal drag. If there is a ton of drag or its locked in both directions, case closed, the pulley is seized. Replace it and go from there. After that we can see if there's another problem remaining.

MedicPatriot · **Posted:** Sun May 19, 2013 12:09 pm

Basically, the noise when I turn on the a/c could actually just be the alternator because there is more power being put on the belt? This is what I am reading it as.

I'm going to replace the thing soon.

CATCRD · **Posted:** Sun May 19, 2013 12:39 pm

MedicPatriot wrote:

Basically, the noise when I turn on the a/c could actually just be the alternator because there is more power being put on the belt? This is what I am reading it as.

I'm going to replace the thing soon.

Yes, exactly. But the tensioner or the AC clutch could have been damaged by running for so long with a bad alt pulley. Try the simple test I suggested before buying any parts though.

flash7210 · **Posted:** Sun May 19, 2013 8:53 pm

DOC4444 wrote:

Yes, the dust is very dark red.

DOC

What exactly is this red dust?
My alternator pulley has orangish brown dust on it.
Everything seems fine though. No loose belt tensioner or flappy belt.

DOC4444 · **Posted:** Sun May 19, 2013 9:46 pm

Orangish brown qualifies. Time to replace your decoupler.

DOC

CATCRD · **Posted:** Sun May 19, 2013 10:29 pm

The red dust does not mean 100% that your pulley is bad. As the clutch wears it will naturally shed some dust. Both of mine have some dust and they are fine. The only way to tell for sure is to get the belt off that pulley and see if it is locked in both directions.

Noises - Alternator, A/C Compressor

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