My99

The other day I noticed the battery light and brake light came on at a stoplight. I figured bad alternator. As soon as I took it up above idle or at a higher RPM the light would turn off. And it never became a harsh steady light anyway, kind of faded in and out.

After reading up on here, I decided I'd change out the brushes first. So this evening I did that. I found that the front brush was worn down pretty good, but the rear for some reason had a lot of life left. Went ahead and replaced it anyway. Fired the truck up and backed it out of the garage. No light. Yay! Let it sit and idle for about 10 or 15 minutes while I swept out the garage and re-arranged the cars so that it could charge up. I got back in it to move it and the dang light was on. Bummer!! As soon as I revved it up over 1k rpms it would go out. I drove it around the neighborhood in 2nd gear, 2000rpm+ trying to make sure it wasn't the fact that the battery was low causing this, although from my past experience that isn't logical anyway.

So here I am, wondering what could be wrong. The way it only happens at low RPM, and is never a real bright steady light makes me think that maybe I have a bad ground, which brings me to the point of this entire post - Where/how is the alternator grounded. The wiring that runs to the alternator has 1 connector that comes out of the harness that runs to the post, and then the only other connection is the large plug.

Anyone have any similar experiences and find a solution?

Also, is there a good way to get a read with an volt meter on the voltage the alternator is putting out at idle?

Thanks!

PlugItIn

theres a ground that connects to the PS pump bracket i believe. Also check the ground on the back of the valve cover to the body itself...

My99

I do think I have the ground on the valve cover going strong... but I do not have a ground connecting to the PS pump bracket. Where does it attach to on the alternator itself?

abecedarian

... and how many times have I said that replacing the brushes may not solve the problem?
Yeah, it's a likely cause, but not always the fix, unlike what some people think that replacing brushes on the alternator or starter are going to 'miraculously' solve the problem.

People forget that the regulator has control over what those 'brushes' they just replaced, those in the alternator do.

PlugItIn

i just had my engine torn apart yesterday, there was a ground that connected to the ps pump for something. My trucks not here, so i can't look for you. My suggestion is to make sure everything is plugged in and tight. If that doesnt fix it, take that alt. off and bring it to your local auto store and test it...

desertcox05

i'm betting on the voltage reg. too. with the engine running set the volt meter to vdc., put the red and black leads on the pos. and neg. terminals of the battery. you should be reading around 14.5 vdc. if it's less than that rev the motor and look for a change in the reading on the meter.

My99

Took it back off and into NAPA for a test run with the new brushes. Failure. Ordered a new one. Oh well, lost $18 on the brush gamble.

Doc.Gneoson

had a similar prob(pretty much exactly what you were explaining) i think it was the regulator for me,when i checked it was only charging at like 11 vdc i think, my alternator was in pretty ruff shape as it was so i just got a new one and it has worked perfect ever since

abecedarian

Costs a little bit to buy, but load test equipment can be a worth-while investment.
You clamp it to the battery, dial in a load, and measure the voltage. If the charging system can't maintain voltage with the amps required, something's wrong.

My99

So update - Put battery charger on battery for about 6 hours on 2 amp setting because it was getting weak. Put new alternator, put it on. All is well for day 1. Test it out with the amp meter, measuring 14.45 volts with nothing running other than a radio. Today I start it up after leaving my coffee joint and the battery & brake light are on. They're on a steady full volume "on" unlike the flickering I got before with the bad alternator. I take it by NAPA, dude hooks up his electronics and says everything is fine. Running high 13.8 volts with no load, and about 13.3 with headlights and fan running full blast. He says that checks out fine and there must be something else tripping the switch that's making the charge light come on.

Anyone have any ideas? I verified when I got home that the alternator is putting out about what he said with my machine when I got home, which is 1/2 volt below what I measured when I first hooked it up, but then again, it was fresh off a charger when I measured it last time... Need any help I can get, as I'm planning to take this dude on a road trip this weekend for some camping and fun!

67ghiaTIV

Any updates? My 87 4runner just started doing this today.

Jamie

xxxtreme22r

edit whoa nice way to revive a 1yr old thread. !!!!! ALT and BATT lights are almost always alternator. take alt out and have checked at an autozone. if it passes put it back in and check the wire from the pos terminal to the fuse box. also check grounds. By check I mean clean them up by grinding off and rehooking them up, don't just look at them and say they are "good". Probably a good idea to just replace the entire battery cable as well.

67ghiaTIV

Mods delete this please

My99

Yes - sorry - I did take the alternator back to Napa, spoke with another guy, the guy I usually work with, he ordered me another and swapped it out. No problems since!

My87Runner

so you got a bad alt that was brand new?

My99

No, it was remanufactured with refreshed components. That's how most all starters and alternators are from parts stores. And yes, it failed out of the box essentially. I'm sure "new" from Toyota would have been $400+.

davidm2232

why should this thread be deleted? i just picked up a new to me 95 pu, my first toyota. i have the same issue, and this is giving me something to go on.