HELP! Bad Alternator, or Regulator?

[freeride53]

I didn't continue to run the car... it's been sitting since it died on Sunday..

Took the battery to the store, had it tested. Said that it was a little low but is likely fine.

Got a new alternator and a new belt. Me and my buddy are gonna tackle it this week.

[cgk_iii]

I don't understand why you are continuing to drive the car? You obviously have a charging issue. You're going to ruin your battery if you keep running the car on a low charge, take your battery out and put it on a battery charger, if you smell sulfur than you ruined the battery. A regulator is only 30-40$ And is held on by 2 Philips screws iirc, you're going to fry the alternator if you keep trying to jump start the car.

[uturn]

Spend that money on a regulator to find your slip rings are worn too... you probably need a new battery because you damaged it by running it flat.

[ST1G]

Now trying to get my hand on a voltmeter to see if the battery will read 13.5 V

This sounds like the best next step.


If you pull out the regulator you should be able to see how much it's worn, if it's pretty worn then you know to replace, if not I would have the alternator tested.

Also check to make sure you have good connections on the alternator.

[estoguy]

I'd be checking the regulator first.

Same thing happened with my car a few months ago. The regulator was badly worn. But it also went just shy of 200K miles before crapping out.

[freeride53]

Here's an update.

Me and a friend tried bump starting the car, it didn't work.
Found a neighbor with cables, he jumped my car right to life.

Let the car idle for 15+ minutes. Shut it off, won't start again.

Now trying to get my hand on a voltmeter to see if the battery will read 13.5 V

[freeride53]

^ Good to know. gonna remove the airbox and see how much room I have to play with.

Barry, when your failed, did you experience similar symptoms?

[reelizmpro]

Yes you can change the regulator without removing the alternator. At least you can on an M20, not sure on the M42. Just remember to disconnect the battery first. Brushes are probably worn below spec. Specs are in the Bentley manual but if you never changed it...chances are it's due. Mine lasted 200K before wearing down.

[freeride53]

^ Can the regulator be removed without removing the whole alternator unit?
And what could be signs/ways to check that piece individually?

Also - no means of charging the battery myself...student living on campus and all my tools are 600 miles away :(

[dnguyen1963]

Your alternator/voltage regulator is dead and not charging your battery. Check the regulator first because it can be removed with little hassle. Have you charged your battery and check to see if it holds charge?

[freeride53]

Update!

Decided to drive the car to campus tonight and on my way, everything started going dim.
Headlights and foglights stopped working completely, interior went black.

As I parked the car was struggling to hold an idle and roll the windows up.

Turned it off, and now it wont start again.

Could this be the regulator? Could I replace it without removing the whole unit?

It's gonna be my first alternator or regulator job! During finals week :(

[E30NJ]

Ever figure it out? I'd like to know. :)

[AndrewBird]

The car will still start and run with a bad alternator. The engine just runs off the battery and slowly drains it. Your battery light should have come on though.

I'd check the engine ground strap that goes from the oil pan to the frame rail on the driver side. Also check/clean your battery terminals and make sure the ground is attached to the body well.

There is also a terminal block on the passenger side of the engine bay. Check/clean everything there as well.

Lastly, check the battery voltage. Should be ~12.5v with the engine off and ~14v with the engine running. If it doesn't read 14v when running, your alternator is likely dead.

[Old city bimmer]

definitely sounds like your alternator.

[ST1G]

I had a similar issue and it was the brushes inside the alternator. Cheaper than a new one.