voltage light on dash on - is my alt toast?

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concretejungle

concretejungle

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just wanted to verify. I was driving from one office to another today and noticed at a stop light that the voltage light was on (red light) above the voltage gauge on the dash in the 80. As i hit the gas it would go off, but if i let off the gas it would come back on.

I'm ASSuming this is indicating i'm not getting the needed charge from the alternator? I have not been home to check the owners manual or FSM yet, so i figured a quick post here would let me know.

What do you think?

Bad timing as i have purchased a car and will have it in 10 days. The 80 must have found out i was going to be cheating on her, so she is pissed. Either way, i guess this is a good time to put photoman's alternator bracket to use. :clap:
 
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mine does the same thing but the transmission and brake lights come on as well. I haven't taken the time to sort out what is happening but the car still runs just fine.
 
The light comes on cos there isn't enough voltage across the circuit to turn it off. Confused? You will be, after this episode...

1st check belt tension/condition.
2nd check wiring to alt, starter, batt, dash. Pay special attention to grounds.
3rd check FAQ. I think this has been covered fairly well.
Sears Auto Center will check your alternator in the vehicle for a fee. Many parts houses will too, some for free.
Denso alternators are nearly as bulletproof as the vehicles they're in. But, I've seen my share of em go south.
 
I will check it out. Right now the Alt is covered in PS fluid since i have a PS leak. I wonder if that is what has caused it. I may just clean it up and check belts. See if that does the deed before getting a 130 amp alt.

EDIT: also i looked through the faq and did a search. Maybe i'm not the best at search but it didn't pull anything up to the effect you say is the issue. If you have a link i would appreciate it.

thanks.
 
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concretejungle said:
EDIT: also i looked through the faq and did a search. Maybe i'm not the best at search but it didn't pull anything up to the effect you say is the issue. If you have a link i would appreciate it.

thanks.
Click to expand...

My apologies. I'm remembering something that isn't there.
But it should be. Maybe this thread'll remedy that.

P/S fluid will damage an alternator. Eventually. It'll attract dirt which will eventually complete a circuit where it's not supposed to. Some brake clean should get it off there fairly well.
I'd bet that's causing belt slippage, too. The fluid will swell up the belt if it soaks long enough. Have a spare belt on hand cos if it soaked long enough, it will fail. Again, brake clean and compressed air will delay the inevitable.

If you've got a digital multimeter, check for a difference in voltages between the battery and + terminal on the alternator. More than a couple of volts and you're looking for wires. Also check for AC voltage between the battery terminals. More than .5V and your alternator is on its way out.

Normal charging voltage at the battery should be 13 - 14.5V at idle.
With high beams, full A/C, rear defogger and interior lights on, at 1500 - 2000 RPM, it should still be over 13V. (Don't rev it that high for too long. Just get the readings.)

Have your battery load tested. A marginal battery will kill a good alternator. A bad alternator will kill a good battery.

Hope that helps you figger this out.
 
If you have an original alternator and not a rebuild Do no let it go, first thing to try is new brushes, cheap, easy to change and fixes most problems with 80 series alternaors.
 
thanks guys. I checked for a loose ground, and there was one. I tightened it up, sprayed some engine degreaser on the Alt. Light is still on. Also, now the light stays on as before it would turn off while in the throttle. Now it just stays on.

The timing on this just sucks as i have a car on the way, but won't have it for about a week to 13 days. I just don't want to fiddle with this until then. I have a new bearing for the AC pulley, getting new belts and also a idler pulley bearing. Wanted to do it all at once along with the install of a 130 amp alternator with photoman's bracket. If this thing could have held out for one more week......

life i guess.

I will look into it further tomorrow.
 
That is how mine started to go. Do the tests as suggested, and go to Checker, Autozone, or batteries plus and have them do a test. That should give you an idea, and is cheap and easy. It will sure enough leave you walking if it is the battery, or the alternator.
 
i seriously doubt it's the battery as it's a new yellow top optima replaced.....well, about 8 months ago.
 
Uh-oh, I may have jinxed myself. This morning the car quit on me. Lost power after stopping but turned right over and ran again, quit a second time but was fine after that. The girlfriend reports that a similar thing happened to her the other morning. Strange that the lights glow from time to time but the car only quits in the morning, could it be moisture related?
 
My truck doesn't quit. That sounds like a wiring harness issue if i were to guess.

My truck runs fine, just the light is on and i'm guessing my battery is not being recharged as i drive.
 
With your PS leak, you may have gotten fluid on the alternator commutator and brushes. Do as RavenTai suggests: get new brushes and clean things up (especially if there's fluid inside the alt.).
 
concretejungle said:
Tom,

I can replace the bushes? Kind of like the starter contacts?
Click to expand...

Kinda like starter contacts, but of course different. First off, I assume we are talking about your '95 FZJ80 and not an earlier 3FE truck. If so, then just call CDan and order a set of alternator brushes. They are rectangular shaped things made out of carbon and encased in a white plastic holder. They are cheap. You have to pull the alternator out of the truck, but from there it's not that bad a job. Maybe an hour altogether. The procedure is described in the FSM.

Be sure to disconnect the battery before pulling out the alternator!

EDIT: Here's a thread with pictures so you can get a better idea what the brushes look like: https://forum.ih8mud.com/80-series-tech/83354-alternator-brushes-before-after.html
 
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Tricky, thanks man! That's exactly what i needed to see. I'm going now to thumb thru the FSM. Been trying to get ahold of cdan. I'll try again tomorrow.
 
do you all think it's safe to drive like this?

I have cleaned everything up, checked for loose ground. Still the light stays on. However, the voltage meter on the dash has the needle exactly at the same point (about a needle width above center) for two days now. Has not gone down any, nor up.

Can i keep driving around, limited driving, until i can pull the alt and start fooling around with it?
 
concretejungle said:
Can i keep driving around, limited driving, until i can pull the alt and start fooling around with it?
Click to expand...

you do have AAA, right?
Yes. You can drive like this for a while while you collect parts and labor. Keep jumper cables in the rig, JIC.
 
concretejungle said:
do you all think it's safe to drive like this?

I have cleaned everything up, checked for loose ground. Still the light stays on. However, the voltage meter on the dash has the needle exactly at the same point (about a needle width above center) for two days now. Has not gone down any, nor up.

Can i keep driving around, limited driving, until i can pull the alt and start fooling around with it?
Click to expand...


what is the resting (overnight) and running voltage at your battery?

resting battery voltage should be in the mid 12's to just below 13, running should be at least 14.0, if you do not get 14._ retest with the engine at 2500 RPM. if you do not get a higher voltage than resting your alternator is not charging.

If your alternator is not charging then you are running on the battery only, when the battery is depleted you will stop running, the remaining range in the battery depends on its health, state of charge and how many accessories (headlights fan wipers radio etc) you run and how many times you start it,

If you need to drive it once to get it somewhere to work on it then give it a shot see if it makes it, use as little electrical as possible you should not drive it more than that. jumper cables will not be as much of a help as when you have a dead battery, when you jump a car with a dead battery you are then runnign on the alternator, having a dead battery and a dead alternator you would be running on whatever charge you got with the jump and it takes quite a bit of time to bring battery from dead to full charge, also automotive starting batteries unlike deep cycle batteries do not like to be deeply discharged it shortens their life.
 
no wonder my alternator was not working!! WTF! look at all the mud/grease/ATF fluid that had gotten into this thing! :mad::bang:

First removed the battery box and battery. I have it on a trickle charger right now :o THen unbolted the PS resevoir for better acess. Also pulled the dizzy cap for better access too. Might get a replacement rotor while i'm in here.

I'm going to clean it up better tomorrow with some carb cleaner. THen put a new "brush" in it.

Pics of getting to the alternator along with all the sludge problem i have.
Alternator cancer 001 (Medium).webp
Alternator cancer 002 (Medium).webp
Alternator cancer 006 (Medium).webp
 
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