15+ Volts

[MrMarquis]

Ever since I got my new alternator from Ford, I will get the very occasional battery light; stays on maybe one to two minutes, maybe once every other week. It really hasn't been that frequent.

Well, the other day when it came on, I checked my UltraGauge for codes and noticed the voltage was at 15.7 volts. The light disappeared when it dropped back below that, bounced a couple times back and forth popping the light on and off, then dropped back into the 13.6-14.4 range. My thought is the light is coming on telling me the system is over-charging.

I'm not really sure how concerned I should be with this problem or if there is anything I really can do to fix it. The few random times I have seen it, it hasn't stayed on for longer than a couple minutes and then I won't see it again for days or weeks at a time. The alternator was supposed to be new and the battery is only a year old as I replaced it last year.

[His Royal Ghostliness]

Have you noticed a pattern as to when the light comes on? For example: engine speed, headlights on/off, HVAC blower on high setting, etc?

[nfldfordltd]

Which vehicle is having this problem?

[IPreferDIY]

I would definitely check with Ford and be looking for a replacement. I don't know if using the prior (presumably bad) alternator with your new battery might have messed up the battery and thereby made the battery the problem, but I'd expect a clear and irrefutable explanation if Ford tried to blame the battery.

[GM_Guy]

All your connections clean? Any terminals you suspect of being loose?
Clean your grounds, again.

Alex.

[sly]

if the sense wire is resistive somewhere, it'll do this.

[gadget73]

+1 on connections, especially the battery sense line. No idea if they changed it, but it used to be the yellow/white wire on the voltage regulator. There was also usually a B marked on the regulator plug. It should tie into the fuse box on the other end.

[MrMarquis]

Have you noticed a pattern as to when the light comes on? For example: engine speed, headlights on/off, HVAC blower on high setting, etc?

Majority of my driving is cruise controlled, highway speeds 55-65.

So I checked the connections and it seems everything is tight. I did note that there was a wire bundle rather pinched up between the fender lip and hood leading from the battery to the alternator. I'm wondering if this didn't break or fray a wire as now that I've tucked it back out of harms way the fluctuation is much more limited.

I'm watching the computer voltage now from my UltraGauge; it will bound between 13.5 and 14.6 volt. Spiked once at 15.2 in the past few days. But nothing as high as before. Also, the computer voltage is at least 0.2 volts higher than the previous readings straight from the gauge, so the spikes when the light came on would have been about 16 originally...

[His Royal Ghostliness]

You got an EVTM for that thing yet? If not sounds like it may be time to obtain one. Not necessarily for this particular issue (tho it would be nice to know what that wire is for), but I got the impression you're planning on keeping the car for a long while, and electrical gremlins are bound to pay you visits every now and then.

[DerekTheGreat]

Maybe the voltage regulator on the alternator is a turd?

[sly]

I'd check the sense wire in the bundle for a kink. Maybe cut and solder back together at the kink and shove back in the happy no kink place. If the sense wire goes through that bundle, it's probably a safe bet that may be the issue.

[MrMarquis]

The battery light had started coming on more frequently within the past couple weeks. Yesterday it came on and remained for longer than before, bouncing between 16.2 and 16.5 volts...

Not wanting to fry the car, I turned it over to Ford this morning. They called after a few hours and said the new alternator was the culprit. So now awaiting a warrantied replacement and the mystery should be solved.

[sly]

stupid bum regulator.

[His Royal Ghostliness]

Electronics... almost as fickle as some women

[sly]

probably a part made by the company I work for.