Alternator or Battery Issue?

[Hill Valley PD]

The last few times I've had the car out, I've noticed it running rough for a while upon initial start up. Battery light illuminates, and volt meter dash gauge displays around 8-9. I have not converted headlights or dash to LED yet, so it is definitely an incandescent bulb for battery light. Once I get car moving and driving a bit, volt gauge jumps to 13 or so, battery light turns off, and car runs just fine. I thought maybe it was a low battery since the car sat for about 3-4 weeks. However, it did it again today after only a week of not being driven. After today's drive, I checked the battery with a volt meter, which read 12.5. It is a NAPA Battery with manufacture date of 08/2017. I crawled under to check out alternator as I don't see a replacement receipt at least for records I have. It's a Valeo that says "Made in France," so I figured that might be it Hmmmmm...

[WHO1DMC]

It's very probably the alternator. The most common problem with a valeo is the brushes don't last a long time.


Dave B.

[Michael]

You can't diagnose anything till you know for sure your battery is good and the only way to tell is taking it for a quick load test. A bad battery can lead you chasing ghosts.

After that, then you can look at the alternator and other known areas like grounds. If you have the time, and since it's relatively easy, you could pull both the battery and alternator at once and have them tested at the same time.

Start with the battery and report back.

[Ron]

It's very probably the alternator. The most common problem with a valeo is the brushes don't last a long time.


Dave B.

+1

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You should see more than 12.5V anytime it is it running. (?~14.2V, ideally?)

The light comes on when the battery is supplying more power than the alternator is giving it -- The battery alone shouldn't turn on the light...

[Bitsyncmaster]

By the way, it takes a long drive to charge a battery that is quite low on charge. If your car sits 3 months and still has the door lock ECU and clock connected it will be about half charged.

[DMC5180]

While it probably is the alternator. It could also be a poor connection in the charging circuit. I know a fellow D owner that experienced a similar condition which turned out to be the main cable connection at the alternator had a bunch of broken wire strands at the crimped terminal ring. Fixing that, corrected the issue.

[Hill Valley PD]

You can't diagnose anything till you know for sure your battery is good and the only way to tell is taking it for a quick load test. A bad battery can lead you chasing ghosts.

After that, then you can look at the alternator and other known areas like grounds. If you have the time, and since it's relatively easy, you could pull both the battery and alternator at once and have them tested at the same time.

Start with the battery and report back.

I have removed the battery and will take it to get tested first and then go from there. If alternator is no good, any suggestions on which one to replace it with? Thanks for input!

[Hill Valley PD]

By the way, it takes a long drive to charge a battery that is quite low on charge. If your car sits 3 months and still has the door lock ECU and clock connected it will be about half charged.

Good point. Longest I let car sit is 3-4 weeks, except over winter when I remove battery and put it on a maintainer. I still have door lock ECU, and my original clock is connected but only works maybe 20% of the time.

[David T]

On initial start-up on some alternators, they won't start to produce electric til the RPM's get over 1500-2,00 RPM's. If you have the "Ducey" (the one from France) I would just go ahead and replace it. While it can't hurt to have the battery tested, I don't think that is your problem. The Ducey is known to fail, the Delorean vendors have better bolt-in replacements now. Or you can live with it the way it is, it really doesn't hurt anything till the Ducey finally goes completely bad. I also recommend a Battery Tender for when you aren't using the car. Also a battery master switch. Improving the Door Lock Module will reduce the parasitic standby drain or you can just disconnect it.

[Michael]

On initial start-up on some alternators, they won't start to produce electric til the RPM's get over 1500-2,00 RPM's.

Yeah that's known as a bad alternator. If your alternator doesn't "produce electric" until 1,500-2k rpms, you have a rock with a pulley on it.

I have removed the battery and will take it to get tested first and then go from there. If alternator is no good, any suggestions on which one to replace it with? Thanks for input!

I have had at least 3 alternators on my car trying to get an acceptable charge rate on my volt gauge. I just learned to live with it. When my last one took a puke I decided to have mine rebuilt rather than buying another. Once I got it back not only did it cost me less than 100 bucks, but I finally got 14+ volts on my battery and even at idle with lights and ac on, was still over 13v.

The place I took it to has been in business of doing just alternators and starters for over 25 years. This wasn't some fly by night hack job or done by some "Jack of all trades" place. If you have the Motorola alternator, I would highly suggest this route because like I said, I never got a good one from the vendors.

If you have a Ducellier alternator( at this point I can't imagine any driver still does) like guru said, replace it with a new Motorola. If I were in that situation, I would go with Delorean Industries. Josh's parts may have a nice price tag but they are also uncompromising when it comes to quality and a crap alternator will cause nothing but problems down the road.