Alternator Light - it likes to shine!

[3D914]

Well guys,

I followed your advise, and now I'm in up to my neck in this alternator light thing. Help!

Originally the car has been running, and the alt light would go out when running, but I was only getting 12.5 V.

So I replaced the alternator (Bosch rebuilt), and the Voltage regulator (Wells VR650). The battery was charged and load-tested at FLAPS and is OK (12.65 V).

I drive it to work today & a meeting this evening. Light still won't go out under any circumstance (except when key is off).

I jumpered from Batt+ to DF on relay board - light stayed on when running.
I jumpered from DF to D+ on relay board - light stayed on when running.

I even tried jumpering between DF & D+ at the back of the Alternator connector that plugs into the relay board - same results.
I thought that perhaps the Relay Board is a factor here - possibly?

When I installed the alternator, I check continuity & shorts on the three wires in the connector. They were OK. The other lead goes to the starter-solenoid, then to Batt+.

Where is the ground for the alternator - the case?

Also cleaned all grounds, and connections at ignition.

What else can I be missing here?
Got a track event this weekend that I've missed two years in a row, and I'd really hate to miss it again.

TIA,

[Amark]

You should have 12 to 12.5 volts at the battery with the engine off. When the engine is running you should have over 13 volts at the battery. Mine reads between 13.5 & 13.7 with the engine running.

Your explanation doesn't say whether it is charging or not. You could have a fault in the wiring that is turning the light on even though it is charging.

[philinjax]

Jumpering the wires as you have, the alternator surely ain't charging the batt. First thing, make sure the wires from the alternator and the blue wire from the Gen Charge Lignt are connected exactly as shown on the wiring diagram. Then the alternator should charge and the light should go out.
If this doesn't correct the problem, then the alternator or voltage regulator is faulty.

Good luck at it,

Phil

[John Rogers]

I'd recommend checking the resistance of the large batt wires and connectors both + and -. If they are very old they can cause the voltage drop you see. I have also seen "rebuilt" alternators, even Bosch not have enough output to do the job. I'd have the one you just bought load tested. Good luck

[Dave at Pelican Parts]

The alternator does ground through its case to the mounting bracket, to the fan shroud, to the engine case, to the transmission case, to the tranny ground strap, to the chassis, to the battery ground strap, to the battery (-) post. Dirty connections at any of those can cause some problems, but more like "the light glows dimly sometimes"--not "light is on bright all the time".

Try digging through the "Charging system troubleshooting" article in the Tech Articles section of this website.

--DD

[3D914]

John,

I did check the connector at DF, D+, & D-. Also for shorts between them. They were good. I'll double check the others that you mentioned.

Since the system was working previously, I didn't consider the Indicator Light. But decided to check that this morning and found it to be 1.2W. I swapped it for a 2.1W. No change.

I suspect your possibly right about the rebuilt Alt. I'm going to pull it and have it tested.

Dave, I'll also double check the ground from the case to the Batt-. Is the D- supposed to be a ground circuit?

Can I check the voltage between DF & D-, then also between D+ & D- and compare them? I have access to the wires through the back of the connector at the relay board.

Many thanks.

[914GT]

D- is grounded according to the schematic. I'd think measuring D+ referenced to ground or to D- (should be about the same) would indicate why the light is on. If it's dropping a few volts below the battery voltage than the alt. light's going to start coming on.

[3D914]

Thanks guys for all the tips.

You're never gonna believe the source of the problem. I'll post a long topic once I get my pictures uploaded from the camera. Watch for new topic: WARNING!-Bosch Rebuilt Alternators!!