Joust

my truck has had the charge light coming on since I bought it. it is intermittent light sorta thing.

today I put my digital multimeter on the lighter socket to monitor the voltage.
when I left home the voltage was 14.25vdc and the charge light was on.
it was like that most of the way to work.
then the lights went off (normal Dash display now) and the voltage jumped to 16.25 and it slowly creeped up and actually touched 18vdc by the time I got to work.
when it touched 18v the abs light flickered on. once I got to work i verified on the battery directly that the voltage was high and it was.
i'm thinking this has to be a problem with the wires that go into the side of the alternator.
I'm looking in the FSM and cannot see where these wires go.
any ideas?
ps
i rebuilt the alternator with new brushes and had it tested. then I put it in with new belts. its working fine. too fine id say....

*Dr. Evil*

Probably the voltage regulator. Sorry, im new to these beasts. Couldnt tell you if its in the alternator or not.

Joust

the regulator is built into the alternator.

blaiwayw

I had the same issue on my 86 22re. Battery voltage would go to +17vdc with the alternator running. Took the alternator to the parts store, checked it for free. Failed all tests. New alternator now charges to 15.5vdc.

Two weeks later, I had to change my battery. Figure it overcharged to long.

WB

mmcpeck

Yeah I'd say it's the voltage regulator which, as was mentioned, is built into the alternator. I wouldn't drive it too much until you either get the alternator rebuilt or get a new one and replace it, because running those higher voltages can hurt other things other than your battery.

Joust

but that's the thing.
I just replaced the brushes and had the alternator tested at a NAPA on a pretty elaborate machine. it passed all tests.
unless its intermittent.
and why, when the voltage is correct. is the charge light on???
i would hate to buy a replacement alt and find the same problem. I'd be out $300. But I'm leaning that way now

Joust

I ordered a new Alt.
What concerns me is that when the thing is working properly (outputing 14.25Vdc) the charge and Parking brake lights are on. When the lights go out, the alt is outputting too much voltage. I cannot explain that....

abecedarian

the lights are operated by the regulator. so the light is on until the regulator comes up to what voltage it thinks it's supposed to be at.

Joust

I don't believe that to be true.
i'm measuring the voltage with a Fluke 79 multimeter. it Measures 14.25V with is proper. the battery light is on.
something is telling the computer to turn on the battery light. When the voltage is too high the battery light goes off. I think there is a voltage drop between the battery and the sense to the computer somewhere so the computer sees a lower than actual voltage.

abecedarian

The charge light is supplied power by the ignition switch and grounds through the regulator.

Joust

Well,
I fixed it.
I bought the new Alternator to install if my suspiciouns turned out to be wrong.
but, they were not. I was right. the White "sense" wire going back to the regulator had a knick in it and corroded right through. I put a splice in it and put it all back together with confidence and fired up the truck. It works like a charm.
The regulator was just fine.

4runnerguy

srry for the hijack but whats the diff between having a relay or no relay on 4x4 lights

abecedarian

the nick was causing the regulator to improperly sense the voltage.
but if you're worried, check your wiring diagrams.

Joust

yeah, i determined that before i cut into the truck. i just could not find where the wires went. I knew it wasn't the regulator. well really it was. the regulator cannot regulate properly if it has not feedback.

4runnerguy,, please start a new thread and I'll explain it.

abecedarian

joust- I think we were going at the same problem from different directions.
I stated the regulator controls the light, which is true, but the nicked / corroded wire was introducing resistance in the circuit thus causing the regulator to incorrectly sense the voltage in the system and consequently causing the lights to light and the overcharging condition.

If it's all fixed, all is good, no?

Joust

yep, it seems to be.
i only run the truck for a couple minutes but it looks good. warning lights off and voltage is spot on.

abecedarian

I'd be inclined to say that if at idle the voltage is good and the dash lights are off, everything's working, considering before the voltage was good and the lights were on.

cheers.