I figured I'd better start a new thread.

In November my alternator croaked. No warning lights or anything. I was driving home from a client and I kept thinking the headlights sure weren't as bright as I remembered. Just as I was pulling into the drive it started to throw weird codes, like ABS faults. The next day I checked and the battery was very low. I charged it, took it to the shop and put the tester on it. Very low voltage from the alternator. OK, time for a new one.

I replaced the alternator with a rebuilt Bosch unit. It worked fine. Up until January 29th, when the battery light came on and the "Battery Not Charging" message came up. I put the tester on it and, sho' nuff it had no alternator voltage. AYKM?? Ordered warranty replacement.

Before ordering the warranty replacement I disconnected the plug from the alternator and checked the middle wire, which I think is supposed to have 12v when the ignition is on. It did have almost 12 volts (battery was down to a bit over 11v at the time). Fuse 5 on the LH fender fuse box is also intact. So, gotta be the alternator, right?

Today I put the new alternator in (Tip of the hat to @michaelh for telling me the manual was wrong and you don't have to pull the fans to change the alternator), fired up the car and, still had the message and light. Grrrr.

Put on the tester and everything is working, alt is putting out the proper voltage and everything checks out. Using 2 DMMs, I tested the voltage at the jump point under the hood (14.2-ish), and at the battery (13.9-ish). So, about a 0.3 volt drop. Not bad. Double checked the transmission to body ground and it looks good and is not corroded. Checked AC ripple and it's bouncing between 0.12 and 0.2x. Some sources say that's OK, others say it's too high.

So... questions are: How much AC ripple is too much? Is there a leaky diode? And what triggers the warning light? Does the computer see the warning light and that triggers the not charging message? Above all, did I get another bum alternator?

Man these cars can be frustrating.

 

These vehicles often struggle with aftermarket alternators. Always best to have your factory alternator refurbished with the proper Denso kit....

 

^^ +1

Agreed, unless there was a high resistance somewhere in that line.

Now that's something I've never checked I wouldn't have thought 100-200 mV would be excessive: depends on state of battery charge & load. Curious now so I'll 'scope mine when I get to the replacement job.

The alternator outputs a 'charging' signal on the 'L' connection (Pin1) which the instrument cluster consumes to produce a message in the event of a fault. You've not necessarily got a dud alternator - just a 'wrong' one as Jon89 alludes.

Is this latest alternator the same as the previous?

 

bosch remans are coming out of sweatshop facilities like all the rest…the guys in there don’t care enough to put the right regulator in.

splice b+ feed to the charge light line and the message will go away


reman denso is 210-0431, new denso is 10211-7633

 

What a drag! Now that you have practice how long does the alternator swap take you?

 

Yes. Unfortunately the original was long gone by the time I acquired the car. It appeared to have a Denso rebuild from about eight years ago.

 

Sigh. I've used Bosch in my BMWs with good success. But, come to think of it, I think they were new, not rebuilt. We contacted the sales guy at the distributor and he said they get quite a few Bosch returns, so I think your opinion is well founded.

Thanks for the part numbers!! I spent some time with Mr. Google and found that the new ones have been discontinued by Denso and there don't appear to be any left. But I did find a company that sells the regulators for about $30. All I could find previously was Jag dealer-only ones for $250. Ouch. As the thing is still under warranty we'll try one more time, using a different brand. The distributor said this other brand has fewer returns than the Bosch. I'll post name and results tomorrow or Friday.

If all else fails I'll try your wiring trick. So, that's splicing the charge light wire into the B+ terminal? The big stud?

Oh, BTW, the P/N 210-0431 shows a unit with the stud on the bottom edge of the unit. Will that one work? The P/N for the one that looks identical to the one that came off the car is 210-0421.

 

It now takes maybe 30 - 45 minutes. I have to pull off the intake pipe and the air cleaner. Undo the top bolt and release the belt. Then underneath, remote the air duct, disconnect the wires, remove the bottom bolt, and, using a big pry bar, wiggle the thing loose from the bottom. Then I have to use a bolt, a socket as a spacer, and the nut, and crank that stupid spacer back. Up top I have to remove the air cleaner box bracket and the alternator will come out the top if you hold it in exactly the right way.

 

my bad it’s 421

no you splice the small ignition feed, it’s the only other wire going to the regulator connector

 

Oh, OK. So, essentially disconnect the idiot light wire from the alternator pin and splice it into the exciter wire? Is that correct? Effectively feeding 12v constantly to the idiot light circuit and eliminating pin 3 from the equation?

Sorry to be so dense.

 

All diode faults show as glowing warning light but you must check at night as some cause a very small glow. That includes warning light on with igniton off Should last 60 to 100 K

 

Replaced the alternator again, with the brand recommended by the distributor. It seems to be working fine, and no lights and no message.

Now to tear into the leaky A/C hose. Man, this car is a barrel of laughs.