Alternator Going bye bye?!?!?

[SharkTech]

Okay, recently I had a belt squeal, here and there, just when starting my Euro S powered 79 5spd 928. It would go away quickly, especially with a few blurps. Now, this got a little worse and one morning snap, there goes the alternator belt, batt drained, etc. So, I checked for leaks around there, if the belts were getting wet, etc, nothing. I recently did a full coolant overhaul all new hoses, etc, everything is very dry and tight including WPump so again no leaks getting belts wet. So, figured okay, alternator belt was on its last leg, it was telling me before it snapped and bam, there it went. Ripped out the belly pan and proceeded to take off all belts as you unfortunately have to do since the alt is in the rear, closest to the block. Replaced all the belts new, put everything back together, voltage seemed a little low but figured since the battery had to get me home after the snap then sat for a while it was tired needing to be rejuiced. Now, after belt break in, all seems well and tight except that squeal came back, again just during startup, few blurps and gone. Now the voltage gauge reads a little low, between 10 - 12v. Now, while belts were off I spun the alternator pulley by hand, very freely, no resistance, lockups, etc, felt perfect. Is my alternator going/should be replaced ASAP or is there something else I am overlooking?!?!?!

Thx for any feedback here, standing by...

[Danglerb]

Belt squeal or bearing?

Hook your battery to a charger and put a full charge on it, and test it.

Sometimes a battery with a bad cell makes an alternator beat itself up trying to charge it..

[SharkTech]

Definitely a belt squeal, typical screaming, etc. Battery is brand new, car starts with no hesitation, like a half of crank, literally.

[Danglerb]

If the pulleys are clean and belt is tight, something is wrong with the alternator.

[SharkTech]

If the alternator is "going" will this cause slight resistance causing the belt to whine like that? Possibly lock up causing the belt snap, etc? Just do not quite understand, figure the alternator is like an off or on type of deal, works or it does not??? Again, shaft had no play, free spinning, etc. Hmmmmm...

AND, yup, pulleys look great and ALL the belts are properly adjusted with correct slack and what not, thx Dangler...

[MPDano]

How about disconnecting the electrical leads to the alternator itself and take it for a spin with ALL accessories off, make sure your battery is fully charged. I don't want you to get stuck somewhere. Report back.

[SharkTech]

Yo Dano, I am not quite sure I understand what this will get accomplished or uncover, or what info you are looking for here? As I said, the belt whined then snapped and I lost stereo/voltage gauge, lights, etc and shut everything down and did make it home, about 7 miles actually, no problems. Then, once all belts were repaired now my whine is back, obviously coming from the alternator belt cause I could not duplicate the belt noise when the alt belt was off, revved quietly, well at least in the belt section. My battery is brand new, and starts the car right up no hesitation. It is like everything is working exactly the way it should after my repairs, except that little whine is back upon start up and my batt volt gauge is under 12. Just do not want this to be an ongoing issue and the belt snap again having me ehad back home with fingers crossed, ya know? Very strange, unless my alt is about dead, but would it do the job its doing if it was just about gone???

[MPDano]

I was just wondering if the belt would squeal even without any type of load on it. If it still squeals without doing anything (charging) then it's time to chuck it in the ocean. Oops, the tree huggers would want me to say, "dispose through an authorized e-waste site."

[SharkTech]

haha, gotcha. Anyway, this belt is brand new, does not look damaged at all so far, and again the other alt belt looked good too but squealed and snapped anyway, seeming like this one is heading in that direction. Just seems to be pointing to the alternator. So, guess I will disconnect the power leads to the alt to see if it squeals, etc without any load from charge, etc.

[MPDano]

exactamundo!

[SharkTech]

Where should my voltage gauge be in a perfect world???

[Danglerb]

If your battery is good, fully charged, why did the stereo etc. turn off when the alternator belt broke?

Without an alternator you should still have more than 10v, but I don't know exactly what might be correct.

Pay no attention to the voltage gauge in the pod, too many issues. Put a meter on the battery or the jump post and measure the voltage.

[SharkTech]

The belt snapped the day before, I smelled a bit of rubber, did not think much of it. Then, the next day I was taking the car to work, and as I leave early, needing lights, etc, also had a little climate control running, stereo, etc. I noticed that my dash lights were starting to dim during my drive, stereo started getting crackly and then the headlights starting dimming, etc. That is when it dawned on me that the day before I smelled a little rubber and also did NOT hear the squeal that morning. So, pulled over, popped the hood and saw no alt belt. Killed all electronics and ran the car back home again making it the 7-8 miles I had to go. Once home the car would not restart. After the belt overhaul, put the car on my land rover for 2 seconds jumped and it started right up, drove it a bit and held a good 10-11 volts on gauge. But, again, the squeal starts back up during fresh cold start only, then gone with a few blurps, blah blah...

[seans 928s]

I am new to the 928 car but, Mine is an 85 and the volt meter holds right at 12. Low for what I am used to but the stereo and everything work fine and the battery always starts the car strong.

[Danglerb]

Sometimes I think the pod gauges are purely amusement or torment devices that depend on sun spot activity.

With a full charge and no load the battery should measure about 12.8v at the jump post or directly at the battery terminals. A voltage different from the battery terminal voltage means a poor connection, dirty contacts, or bad wiring.

Some tests may say a fully charged battery showing 12.5v is still "OK", but I have seen replacing such a battery with a new one and no other changes fix problems.

I think it puts an abnormal strain on an alternator to recharge a battery that has been drained down, so unless I have no choice I put a battery charger on it before driving.

[Alan in AZ]

You should be generating 13V-14V at 1000 rpm. The way an alternator works is that for a given electrical load it will load the engine the most at the lowest rpm. So Idle is your worst case belt loading. Its quite possible your belt was just not tight enough and that slippage at idle damaged the belt - the burning rubber smell suggests this too - belts don't burn before they break unless they are slipping/rubbing...

If the belt was slipping the alternator would not generate 10-12v & means it was generating nothing...

So your alternator belt needs to be really tight....

BTW don't rely on the pod guage - use a DVM on the jump post.

Alan