Bad Alternator?

[NTIMD8R]

I was driving home tonight in my '04 3 hatchback and downshifted to pass a car in front of me. The car revs up to above 4000 rpm and I notice the needle on my voltmeter drop from 14V to slightly below 12V and the headlights dim. I leave it in 4th and it stays around 12V. I shift into 5th (around 2500-3000 rpm) and it goes back up to where it normally sits, slightly above 14V. I test it again and it does the same thing.

What would cause this? It has to be the alternator or a part inside the alternator (ie voltage regulator) doesn't it? My 3 has almost 111,000 miles on it so I figure the alternator has lived it's expected life and is about to give up the ghost. The belt does not appear to be slipping and the battery and tensioner have been recently replaced. Anybody have any insight on this?

FYI The charging light has NOT come on in my car. I'm just going by what the voltmeter reads. It has never had this much of a noticeable drop in voltage before. The alternator's still charging if the voltmeter reads 14+ volts, isn't it? Why would the volts dip when revved? You'd think it would be the other way around...

Any help/insight would be greatly appreciated!

 

[NTIMD8R]

40+ views but no replies...

FYI, I told the above story to one of the mechanic supervisors at work and he immediately said that I have a diode going bad in the alternator and that I need to replace it. I figured that was what was wrong but I just wanted confirmation that the alternator was the problem. Nice to have that.

Got a remanufactured alternator with a lifetime warranty from one of my customers on my route; list price: $387, price paid: $205 (headbang) Woo hoo!!

Will install this weekend. Old one is still hangin' in there as long as I don't get on the throttle or sit at idle with the brake pedal depressed.

 

[NTIMD8R]

New alternator installed. No more voltage problems! Works like a charm! Old alternator being turned in to get that damn core charge back...

 

[djltoronto]

Thanks for sharing.

 

[ohioan]

Hey was that hard to install? with the tight squeeze and all? Would the speed have the same setup?

 

[NTIMD8R]

Was REALLY easy to install. The alternator on the NA 3 (2.3L) is located on the lower front side of the engine block and is really easy to get to once you remove the lower splash shield.

Alternator Removal

1. Disconnect negative cable from battery (trust me, do this!)
2. Take off lower splash shield
3. Remove accessory belt off of alternator by moving belt tensioner
4. Disconnect cable from alternator by removing nut, then cable
5. Disconnect plug from alternator
6. Remove alternator by removing the four (4) mounting bolts holding the alternator on to the side of the engine block

Installation is reverse of removal...

Not sure on where the alternator is located on the MS3 but that's the way it's done on the NA 3 (2.3L). Hope it's as easy for you!

 

[ohioan]

It looks like it's crammed down on the side of the engine.... We'll see!