Battery light on can't determine why - safe to drive?

S

Steve240

Member
My battery light came on the dash Monday morning, at the time the truck had been idling for awhile so my first thought was loose alternator belt. Either way drove to work - light stayed on - drove home light stayed on. No issue's with the truck other than the light on.

Last night I checked my battery: with alt on - 13.78, alt off - 12.6. My charger also has a alternator check which passed, i'm not 100% sure how it checks it though. So bat and alt seem normal. I cleaned all the contacts, at the battery the grounds from the engine, fender, and the ground to the alt. Light is still on. I drove it to work again today and checked the battery with the multimeter and everything seems good. I've now put 210Km on with the light on and see no issues. I'm sure if I don't do anything this is going to leave me stranded at the worst time.

When I have the time, probably this weekend I will pull the alt and get it bench tested, alt is 2.5 years old (toyota reman), bat was new in oct 2013.

Looking for some advice for what next to check and also if this safe to drive. I'm thinking if the voltage reg is f'd it might be charging full all the time, will that do any damage?
 
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Sorry what do you mean by turn in lights, heater, etc?

And what voltage should I see at idle vs 1500 or am I just checking to make sure it's constant?
 
thats a little low, i just tested mine and it was around 14.6 with no load, and with my head lights on and driving lights it was at 14.4-5 at idle, i didnt test it up at 1500rpms though. check your wire harness plug on the back of the alt, inspect the wires for any cracks or breakage either in the wires themselves or the insolation in the wires. i have had my battery light on for the last week or so, but ive been charging just fine, today i finally went out and inspected the harness, i have a small break in the insolation on the white wire, and when i moved the wire itself to another position the light on my dash went out. also my batter was at 12.8v with the motor turned off and the lights still on. so your battery seams to be fine.

id say if your alt is charging in the 13v range or lower then its on its way out. densos like to charge a little high closer to the low to mid 14s. but id check for a broken or lose wire off the back of the alt before id go looking to replace it, and id also check your connections at the battery and the alts main terminal, clean those up good and your charging might come up a little as well.
 
^ exactly right thanks. I went out and checked for the wire and it fell out of the connector. Looks like a pia to fix. What does the white wire do beside's turn on the battery light. is it okay to leave that broken until the weekend?
 
I'd say fix it as soon as possible. It could be the excite input and with it not connected the voltage regulator may not operate properly.
 
Steve240 said:
Sorry what do you mean by turn in lights, heater, etc?

And what voltage should I see at idle vs 1500 or am I just checking to make sure it's constant?
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The alt puts out more current as the rpms increase, that's why the 2 measurement points. If all is well with the charging system the change would be fairly small.
The minimum voltage for charging is 13.8V, but 14+ is better.

Turning everything on creates a large load on the alt, and again, on a good system the drop in voltage should be fairly small.
 
Sounds good, thanks everyone. I'll deal with that wire on the weekend but I appreciate the pointers. I feel more confident having to drive the truck at night now that I know it's just that wire.
 
Steve240 said:
^ exactly right thanks. I went out and checked for the wire and it fell out of the connector. Looks like a pia to fix. What does the white wire do beside's turn on the battery light. is it okay to leave that broken until the weekend?
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Steve240 said:
Sounds good, thanks everyone. I'll deal with that wire on the weekend but I appreciate the pointers. I feel more confident having to drive the truck at night now that I know it's just that wire.
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i have to give credit where credit is due, [MENTION=94888]EatonKyleH[/MENTION] gave me the pointers just the other day on the white wire, and told me its a fairly common problem, so i figured id just regurgitate that info back at you, glad it worked, but dont really thanks me, thank him.

electrical is not my strong point, i can do it and understand the basics but trouble shooting it is beyond me, i need someone to almost hold my hand and baby step me through it thankfully there are some really good guys here that can do stuff like that. glad we could be of help
 
the kid said:
i have to give credit where credit is due, [MENTION=94888]EatonKyleH[/MENTION] gave me the pointers just the other day on the white wire, and told me its a fairly common problem, so i figured id just regurgitate that info back at you, glad it worked, but dont really thanks me, thank him.

electrical is not my strong point, i can do it and understand the basics but trouble shooting it is beyond me, i need someone to almost hold my hand and baby step me through it thankfully there are some really good guys here that can do stuff like that. glad we could be of help
Click to expand...

awe shucks! thanks man.

lol, just glad this info helped a few people in short order!
 
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