Alternator light

[frederik]

Hi all,

I’m currently on a trip in the Scottish Highlands (which is truly amazing btw) and unfortunately have ran into a little problem. At the end of the afternoon at our hotel, I have attempted to fix my intermittently working tacho. This was caused by a bad connection at the engine connector at the rear of the fuse bay. I’ve taken apart the connector and tried to fix the connection but couldn’t solder it so that wasn’t very successful. So all the little female connectors were out of the black plastic housing and I put the back correctly afterwards.

After dinner, we decided to go for a bonus drive on empty roads. But my alternator light wouldn’t go out after starting. Above 2-3000 rpm, it glows dimly and when idle, it is bright. My voltage at the battery is 12.5v at idle, and 14.4v at 3000 rpm. Of course I suspected my connector work because that was the last thing I did, but everything looks good there. The blue wire goes to the alternator but the connection is good. And if I remove the connector, the alternator light doesn’t illuminate on contact which proves that this connection is OK.

Now I have had this problem before, about two years ago, and at the time it was caused by a bad ground at the alternator. I could remove the alternator again and check the ground, but it seems odd that this would happen suddenly, and it’s a lot of work. Does anyone have any thoughts about possible other causes? Could there be something else with the engine harness connector?

I’m not too worried about driving on because the battery is still charging at 3000 rpm+, but it’s just annoying to have to look at the glowing light all the time. Thanks!

Pic for attention

[frederik]

Oops... looking at the wiring diagram again, the wire that was bad at the engine harness connector is the brown one and that is the ground to the alternator and regulator. So I need to properly fix that one to solve this problem.

The tacho wire is the black/violet one so that must be something else altogether.

[frederik]

So, made it back home safely. Yesterday I repaired the brown wire at the engine harness connector properly, but it didn't solve the problem. Removed the alternator, checked all connections, made a better ground wire there because the original looked sketchy. That didn't fix the problem either: still the alternator light didn't completely go out even at higher RPMs. Removed the alternator again and brought it to a local shop, where the friendly owner explained to me that since it's a newer alternator with a built-in regulator, the fourth "W" connection on the alternator should not be used, and CERTAINLY not connected to the ground, because that basically shorts part of the alternator. That explained the large current going through that wire. Hooked it up correctly and problem solved.

So what happened is this: the shop that restored the car (for various reasons I no longer go there, and this is just one more reason) put in a new alternator with built-in regulator, and connected it just like an original alternator. That caused the brown wire to burn out at the engine harness connector, so after that everything worked correctly. Until I noticed this on my trip and restored the connection. What a total mindf*ck...

[NorthernThrux]

Good detective work though!

Ravi

[frederik]

Thanks!