alternator at 19 volts

[pinellasproofer]

Hello, I’m new to the forum and would like to say thanks beforehand for any advice you can give.

My daily driver is a ’78 Scout II with the 304 and manual transmission. I’ve driven it for more than a year and the electrical system conked out on me after 40 minutes in stop-and-go traffic. It’s probably the bulkhead connectors, but I took it to a shop before finding this forum.

The shop told me my alternator was putting out 19 volts, and I needed to get a new one. I took it to auto zone since it has a lifetime warranty, and it tested fine. I took it to advanced auto, and it tested fine. I took it back to the shop, and after $200, they told me the harness was plugged in backwards even though the plug tab was pointing the correct way. Of course after driving it home with the plug the “right way,” I noticed that the alternator was not charging the battery enough. The battery was dead by the time I hit my driveway.

After reading the alternator sticky in the forum, I think the shop is wrong since the “wrong way” matches the pictures. I tested the alternator myself with the plug the “wrong way”(see photos) and it is indeed putting out 19 volts. Before I start messing with wires, is there an obvious reason for this? At some point it looks like someone clipped a lot of wires and had a dual battery setup, but I only have one battery in it.

I plan on ditching the bulkhead connectors and redoing the grounding on the engine block. I don’t think the remote starter installation would fix the alternator, but would it be worth a try? I also am replacing the crv behind to the gauges to try to get the light behind the fuel gauge and the gauge itself working correctly (it only goes up to ¾ tank when full). If all else fails, I am going to buy the quickwire harness and have another shop install it since I know next to nothing about electrical.

Thanks again for any help you can give.

Brian

 

[Michael Mayben]

The alternator wire connecter I see in your picture is correct for a delcotron 10si. The smaller diameter wire is the exciter (in the case of the Scout II that is special type "resistor" wire), the larger wire leads to the battery positive post in some manner.

Yes, I can see it's been "repaired". But as long as the original wire runs were followed, that is not a problem.

Adding the secondary starter relay is not a fix for electrical issues, but it is a very effective enhancement to the system and it will correct the "hot restart" issue on some vehicle if the wiring is done properly. And...the starting system is a separate issue from the charging system though they do share some components to a degree.

Any delcotron 10si that produces in excess of 15 volts is defective! Period!

This is by far the most common failure mode on these items...and normally will not show up when the alternator is run on a test stand. It is a fail point regarding the solid-state voltage regulator and is one of the items normally exchanged during a rebuild. I've had 10si failures occur on my own stuff for years where the output was in excess of 50 volts!

Whoever tested the alternator did not test it long enough for the failure to occur, this is so common in these parts stores you can sit in the lot and just watch the folks carry 'em in and out! As for the shop that said it was connected "backwards, they don't have a clue as to what they are doing.

All of the wire runs for the alternator and the starting system need to be tested for continuity, connector integrity, and functionality before doing anything else. Once you are certain everything is correct, then go back and make any needed repairs.

You will find the appropriate wiring schematic for this vehicle in this thread:

http://www.forums.IHPartsAmerica.com/electrical-tech/5408-ihc-electrical-schematic-library.html

 

[pinellasproofer]

Thank you very much for the quick and informative response. Luckily, I can return the alternator.

And thanks for the link to the wiring schematic. I have the service manuals from the store as well. Now I just need to learn how to decipher the schematic.