Charging issue -- intermittent alternator engagement

[kuwacs]

I was taking off from a light, and I heard some strange noises from under the hood. A rattle and squeak or something. Didn't pay much attention to it, as it could have been the car on my left.

Little bit farther down the road, I get the battery light and iDrive charge warning. I turned around, headed back home, and when I pulled into my driveway, all was back to normal, so I headed to work.

I pulled the voltage up on the OBC, and left work. Voltage was pretty stable at 14.5ish, maybe dropping a little when coasting. As I got closer to home I decided to play with it -- I turned on all electrical things (seat/steeringwheel heaters, defrost, blower fan, rolled a window down). Suddenly the voltage dropped to 12.2, and the alternator started making terrible noises. Turned off the accessories, and voltage stayed low.

Parked it, went inside to research, and went back outside to check it out more. Started, and the voltage is back to 14.5. Turned on some accessories, and it drops again, and starts making noise. (Video below)

https://youtu.be/PVN2XvmMsOg

So, should I just replace the alternator, or what?

I'm going to pull out my computer and scan codes in a minute, but I wanted to see if anyone else had some suggestions!

- - - Updated - - -

I think I understand it -- this car has an over-run clutch pulley on the alternator. I think when beefing up the load on the alternator, the clutch is breaking-free, and not engaging to turn the alt. Letting everything cool down probably lets it return to normal. Guess I have to replace the pulley, or the alternator, as I may not be able to source the tools for the clutch pulley.

[bcromwell]

Rotate alternator pulley in opposite direction, it should spin smoothly without the alternator shaft turning
Rotate the pulley in the free spin direction, it should feel smooth not rough

They do go bad but no that often that I know of

[kuwacs]

Rotate alternator pulley in opposite direction, it should spin smoothly without the alternator shaft turning
Rotate the pulley in the free spin direction, it should feel smooth not rough

They do go bad but no that often that I know of

I pulled the belt off last night, and put a screwdriver in the alternator case to hold the fanblades still, and spun the pulley. Wouldnt budge either direction. So I put the belt back on, turned on the car and loaded the alt up again, and it started making those noises again. Turned off the car, pulled the belt again. The pulley was super hot, strange having only run for 4 minutes. But I put on gloves, and put the screwdriver in, and sure enough the pulley spun in both directions. It's on order. And should be here with the special tool tomorrow!

[kuwacs]

So, this is all fixed. To keep this up to date for anyone else who had this issue:

Symptoms?
Battery light. Low voltage. Clunking/squeaking from alternator. It might be intermittent -- for example, my pulley slipped when the alternator was loaded up (HVAC, heated seats, etc), and then giving it a sudden throttle change.

Diagnosis?
Pull off the belt, try spinning the alternator. Nice and smooth? Good! If not, consider replacing the whole alt. Now stick a screwdriver into the front alternator vents gently. Try to turn the pulley counter clockwise with mild force -- the outside of the pulley should spin, but the alternator shaft should stay put. Try to spin clockwise -- it should not turn at all unless the screwdriver/alt shaft moved. If either of those aren't true, your pulley needs replacement.

Repair?
I ordered the tool and pulley from EEuroparts, because they are right down the street from me. The tool is for VW/Audi Bosch alternators. For my Valeo alt, I just needed the spline tool attached to it, and then used an extra long T50 torx bit to remove the pulley.

First you need to remove the alternator. Disconnect negative terminal on the battery. Now remove the airbox. Then youll use an E12 star socket on the 4 mounting bolts for the alt. Loosen, but leave the top two bolts in. Disconnect connectors -- one is a clip connector, and the positive terminal comes off with a 13mm socket. Support the alt, pull the two top bolts, and pull the alt out.

To get the pulley off, hold the spline tool with a 17mm wrench, and turn the torx bit/ratchet clockwise to loosen. Unscrew the pulley from the shaft, and screw the new one on. Tighten to 65lb-ft and reinstall the alt.

Word of caution: I had a hard time finding the right pulley. All three I ordered were wrong, so in desperation, I just installed a new alternator. Try to get the part number off the pulley before ordering to make sure you match it up. Some don't have the same clearance!

Hope this helps. If you need more info, feel free to ask!

-Kyle