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Trying to troubleshooted problems with my Honda

Problem definition and background: Sudden onset of whining noise on a 2007 Honda Accord Ex coupe.

1)Whining noise becomes louder when accelerating.

2)Whining noise is more pronounced when AC is turned off.

  1. Using a mechanics stethoscope, it was discovered that the noise comes on immediately when the AC clutch is disengaged and is greatly reduced/disappears immediately when the AC clutch engages.

4)The whining noise is the loudest at the left end of the compressor or the right side of the alternator. I was not able to distinguish whether one is louder than the other.
Interestingly, however, the noise is not heard when placing the stethoscope on the AC clutch.

5)I tried to put WD 40 on all of the pulleys except the crank pulley and could not come to a conclusion as to whether it had any effect on the noise. The noise seems to be slightly reduced after spraying the compressor pulley but not a 100% sure of whether this is the case.

6)The whining noise is only present in park or neutral mode. It disappears when the gear is shifted to park or neutral (while stationary).

Summary: Whining noise seems to be at the alternator, compressor or somewhere in between but I cannot tell for sure. I tried to apply wd-40 but the results were not conclusive. How can I tell whether the noise is coming from the alternator, compressor, or both or something in between?

Whatever is going on here, I don’t think it can be dealt with through this forum.
You likely need a pro, and I would definitely stop with the WD40.

Remove the serpentine belt and rotate the pulleys by hand to feel for a worn bearing,



It seems to vary with RPM. If you can remove the belt (probably only one, but all if more than one) then put your hand on each driven and idler pulley. Rotate each feeling for roughness/graininess. Try to wobble each and push in and pull out, feeling for any play in its bearing. If there is an idler/tension pulley, try to discern if it can smoothly move to release or increase tension on the belt. Maybe it’s not putting enough tension on the belt. Anything other than smooth movement with no play could be a source of noise.

I tried that. Couldn’t tell for sure, maybe I’ll try again. What type of sound should be listening for?

Yeah, the smell was pretty bad.

No sound.

Feel for roughness in the bearings.


I tried that. There doesn’t seem to be much difference between the pulleys, although the autotensioner seems to jiggle a little bit when the clutch is engaged.

I didn’t feel roughness on the compressor pulley but then again I’m new at this.

It could be the power steering pump

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I had a similar problem with a Ford Econoline. I couldn’t trace noise with a stethoscope. The AC pump was non functional so I doused the moving parts with wd 40 (not the belt or belt area). The noise went away until the oil wore off. I wouldn’t spray oil on a working system because there’s clutches involved, I’m just telling you this to suggest that a stethoscope may not be able to isolate a whining compressor.

I had the car inspected by a mechanic. He said that it is a faulty auto tensioner that is causing the problem. He cranked the tensioner (thus slightly relieving the tension) while the engine was the running and the noise went away.

SO… relieving the tension causes the noise to go away. Then again, when the clutch is engaged the noise goes away (seems that this would add to the tension).

When I’m testing for a belt-caused whining problem I spray a little water on the belt. If the noise goes away the fix is usually to replace and/or tighten the belt. On your car you can’t tighten the belt manually, so I’d guess the best path to a solution is to replace the tensioner and the belt.

Right. Ordered both the belt and tensioner, will report on how it goes.

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I replaced the tensioner as well as the belt and the noise is still there. The noise is a little less intense than it was before but it still persists, especially while accelerating. My guess is that the source is probably a bearing either on the alternator or the compressor since the noise seems to be the loudest at these two locations when I’m using my stethoscope.

Does the noise go away – as a test – when the belt is completely removed? This is the usual method to find this sort of problem. And when the belt is removed all the pulleys can be hand spun, which makes it easy to hear noises associated with one particular pulley, or if the pulley is difficult to spin, or it has axial or lateral play, wobbling etc

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I have not tried this unfortunately.

Guess, I’ll have to remove the belt again.