Replacing the alternator harness

[MyToy]

Hey Tim:

Referring back to your message #66 in this thread you show a picture of the 3 pin connector for the alternator. Is this illustration looking at the male connector of the alternator or is it looking at the female side of the harness? I know it says "plug to alternator" but my wires colors do not match and I just wanted to be sure. A kind yes or no would be very helpful. My machine is down and I am trying to get her back on the road.

Thanks Tim

MyToy

[timsrv]

That sketch is representing the alternator itself (the socket where the harness plugs in). If you're looking at the harness plug, the side that is closest to the alternator, the wires color/function would be a mirror image.

[MyToy]

Perfect! On my way back on the road!! Yippie!

[Jheinz]

So I've been dealing with intermittent christmas dash for awhile. This week I finally got around to checking it out. I had a spare alternator sitting around, so I started by taking it in to my local autozone and had it bench tested. All the checks came back green, so I decided to try installing it. After the install, I saw that my battery was not charging, although I did not have the christmas dash anymore. I decided to pull the harness, and after checking for continuity I found that 2 of the pins were no good. I ordered a replacement plug off of ebay and spliced it onto the harness. Now I'm charging but still have the christmas dash. My battery is at about 12.5 volts when the van is off and around 14v while running. It seems like my 0.5 fusible link is completely bypassed, although one end is still connected to the battery. I've also checked the charge fuse under the dash and it is not blown. Any ideas what could be causing the christmas dash? Here are my current thoughts:

- Perhaps the alternator I put in was never good, or perhaps I damaged it. I did end up shorting out the battery and blowing the 1.25 fusible link due to a stupid error on my part. I'm very much an amateur when it comes to electrical repairs haha. I've ordered another alternator from Autozone that should be here in a few days. Side note: Anybody have a good source on alternators? I know the autozone ones don't tend to last. Worst case I'll probably look into repairing one of my dead ones, or find a local repair shop.
- It could be possible that I mixed up the L and IG wires when I spliced on the new connector. Would that cause the christmas dash even though the battery is charging? Is there any way I could tell that I mixed up those two wires?
- Maybe the fact that the 0.5 fusible link is disconnected has something to do with it. But it seems like that fusible link is intended to protect the S pin, correct? I was reading voltage at the S pin on the new connector. Where is the 0.5 fusible link supposed to connect? One end is coming out of the positive battery terminal, where should the other end go?

Any help would be greatly appreciated. I'm certainly quite a novice when it comes to electrical work, and while it sucks that the van isn't drivable, this is proving to be an interesting project. Thanks to everyone in this community, I wouldn't have even known where to begin if it weren't for all the helpful information on this forum.

[Jan-Willem]

It seems like my 0.5 fusible link is completely bypassed, although one end is still connected to the battery

What do you mean exactly? there needs to be a wire, from the S(ensor) of the alternator, to the plus pole of the battery. It came with the yellow fusible link thingie near the battery. This wire should be direct, the shortest possible route from the alternator to the battery, it should not go to any other positive sources or be shared with any electrical devices on the van.
The idea is that current through a wire causes a voltage drop on that wire. So the alternator needs that wire, to measure the voltage of the battery, without any other currents influencing that measurement.
I thought I had a smart idea once, to put a relay in that circuit, to prevent a slow drain, even that was too much on the sensing circuit, and messed up the proper regulating of the alternator.

[Jheinz]

Doh! I am indeed a fool haha. It turned out that the 0.5 fusible link was in fact connected to the wire that I assume goes to the alternator, while the disconnected end was supposed to be connected to the battery. While the van is running, touching the exposed end of the fusible link to the positive battery terminal causes the christmas dash to go away. I think I'll be up and running once I splice a new ring terminal onto the end of the fusible link. I'll update later today with more info if I have any more trouble.

[Jheinz]

So now I've encountered a new problem. After correctly hooking up the 0.5 fusible link, my problems seemingly evaporated. Until last night, when I got Christmas dash while driving home at night. When I start the van, the alternator seems to be providing normal output. But after driving for only a minute, I get Christmas dash. Voltage at the battery and the plus box indicates no charge from the alternator. Interestingly, unplugging the 0.5 link causes a seemingly correct voltage of 13.8 volts. From what I've read here, without the S wire being connected the alternator will go into "full field mode" which can be dangerous. After shutting off the van for a few minutes and restating, I'm seeing the correct voltage again at idle until I drive for a minute or two. Could this be the regulator inside the alternator? I will probably try installing the replacement alternator and see if that helps. Any other thoughts on what I should check?