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New alternator, still issues


I have a 2006 Suzuki XL7. Recently my alternator stopped working. It wouldn’t keep the car running when we jump started it. We replaced it with a new alternator and now its having the same issues that it did when the last alternator was working and eventually went bad. Here is everything I know, I’m hoping someone can help me solve this problem or tell me what is possibly wrong.

The car held at around 14.6 volts when we first started the car after putting in the new alternator. We turned on the radio, wind shield wipers, and the headlights. The voltage dropped to about 13.4. At this point we decided to drive it. We put the car in drive and only after I gave it gas it started squealing like the old alternator did before it died 3 or 4 weeks later. The car squeals at at a consistent rhythm. Until you give it more gas and it blurs and sounds like one constant squeal. The squealing is far louder when you are actively pressing on the gas. After taking it around the block a few times we tested the voltage once more and it was holding at constant 12.6 after everything in the car was turned off.

I think this is all the relevant information, but here is some brief history just in case it helps.
I had subs in the car, but they were disconnected when the new alternator was put in.
I installed an after market radio. The squealing did not start until long after this.
The battery is fairly new and the squealing with the first alternator was happening before we put the new battery in.
We replaced a broken pulley once, I’m not sure about the timeline on this, but it was before the squealing started.
I had an oil change just before the first alternator broke.
I still have the old alternator if that can tell me anything.

Thanks for any input you can give me, I appreciate anyone who made it even this far!

The drive belt is not tight enough, the belt should not be squealing.

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Yeah or maybe the battery is shot and the alternator is working overtime to charge it until it dies a young death.

Could the belt be causing the alternator issues aswell? Even voltage drops? And it sounds like its the actual alternator squealing.

I dont belive its the battery because it started before I last changed my battery and continued with the new battery and alternator. The battery is like 10 days old.

Yes. The reason is “Maxwells’s Equations”, you can google the topic on Wikipedia. There’s four main equations. Look at the third one

Del X E = -dB/dt ? (“Del” is that upside down triangle)

That’s saying the electric voltage (E) output by the alternator to the battery is proportional to speed the magnetic field (B) changes, which is the same as alternator pulley rpm. If the belt is squealing the pulley isn’t turning as fast as the belt is trying to turn it, and this indeed could cause your measurement of low voltage.

Alright so I’ll just tighten it up and get back to you. Thanks for the advice.

When I think I have a belt squeaking I squirt a little water on it from a spray bottle. If the squeaking immediately stops, a slipping belt is almost certainly that’s the cause. The solution is usually either to tighten it up, or replace the belt. Sometimes the problem is neither the tension nor the belt itself; instead there’s something preventing the pulley from turning freely, such as a faulty alternator (mechanical fault), or the current demand placed on the alternator by the battery and the rest of the electrics (electric fault).

Replace the serpentine belt.

It can’t be tightened. Because it has an auto-tensioner for the serpentine belt, and the serpentine is probably worn. But it doesn’t look like it.


I appreciate all of the help you guys are giving me. The belts are all tight. The tensioner is doing its job and squirting water did nothing about the squeaking. Any other ideas? Also the squeaking only happens under 13 volt. Does that mean it could be an electrical issue?

Update, now it wont go above 11.7 volts ever. Even with no electronics on.

@George_San_Jose1, you geek, you.

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If it won’t go over 11.7 volts it isn’t working at all. Either a connection to the new alternator is not connected or the new alternator no longer works, if it ever did.

Does the noise come from the belt or the alternator? I don’t think your original post makes it clear.

Have you bench tested your old alternator? If not, take it to Autozone, Advance Auto or some other place to have it tested.

Its the alternator squeling, the belts are tight enough and when we first put the alternator in, it was over 14 volts. We let it charge for a bit and then tried driving it. It wouldnt come back over 11.7 volts after that. I dont want to put in another alternator until i find the issue because im worried the car is killing them.

I would get the old and new alternator tested to make reasonably sure that you have a good alternator.

An alternator does not normally make a squealing noise when going bad, but bearing or a slipping belt will. A new belt for your car is probably less than $20. Even if your present belt shows no obvious sings of wear and cracks, the first thing that goes are the V grooves wearing out. Unless you know what you are looking for, there is a good chance it can be overlooked.

Does your battery light come when you hear the “squealing” noise?

Thanks for the response, their is no battery light, and the issue with the belt being possibly bad is that the alternator initially had 14+ volts and now has only under 12 at any time after I drove it. I have also sprayed the belt with water and the squealing still comes from the alternator.

Like I said. Have the alternator tested. Wouldn’t be the first time that a rebuilt alternator is bad right out of the box. Since you just purchased this thing, you should have some warranty.

If water on the belt didn’t affect the squeal, then you are probably right, it’s the alternator that’s doing the squealing. it could be another pulley or accessory on the belt loop making the noise, but since the alternator isn’t outputting the correct voltage, best guess is something wrong w/the alternator at this point. Fix that and you’ll fix the squeal is the plan I think. A faulty battery could load down the alternator so much to cause this, so good idea to have the battery load tested. Many auto parts stores have a test fixture to test alternators, so if your place has one, just unbolt the alternator and have them test your alternator on their test fixture.

What else? The alternator could be wired up incorrectly I guess. But that’s usually difficult to do as the connections tend to only fit one way. There could be something else loading down the alternator other than the battery. Have the alternator output current measured for that. At idle with nothing else electrical on, I’d guess the alternator wouldn’t be producing more than 2-3 amps to keep the battery charged. If you measure 20-30 amps, there’s something in the car putting a really big load on the alternator, and you’ll have to discover what it is. I have a DC amp measuring gadget I bought at Sears years ago, which is really nothing more than a magnetized dial. Very simple. You position the wire in its slot, and it measures the magnetic field generated by DC current in the wire, which is proportional to the current. That comes in handy w/problems like this. There’s digital clamp-on DC amp meters available also.

My guess at this point is you just got unlucky with the replacement alternator. If this is an aftermarket part, not an unusual thing. I’ve had two aftermarket starter motors not work right out of the box.

I installed another new alternator. I gave it a test drive yesterday and I heard no squealing, and the voltage was fine. Today I went to go to work and it started squealing again after I used the windows and radio. At this point I’m convinced its an electrical issue. The battery is new, but it was installed a couple days before the first alternator went bad. I don’t have anything else that is in my skill set to try and diagnose this, and the estimate to get this diagnosed is close to what I was offered at a dealership. Unless someone has something else to help me diagnose the issue, I’m going to trade it in.

At this point I know its not the belt nor the alternator being bad.