Electrical Issues

Hello,

About a couple months ago my 99 Tacoma began experiencing charging issues. The light would come on, turn off, and come on again and eventually came on and stayed on. It was at this point that problems started occurring. Checked everything out and sure enough the alternator was dead. Replaced it and everything was fine, no starting issues and no warning light. Then, today, the warning light came back on. Started fine, drove fine, and when I got home I checked the alt and belt and battery connections. Started up again fine, but light still on.

Hoping there isn't some sinister electrical fault that has killed another alternator, because I can't see anything else wrong. Don't have a code reader, and my regular mechanic is closed.

Any ideas as to what might be happening? Battery is only a year old, and brand new alternator.

 

Time to break out the volt meter.

 

Yeah that's my next step.. Hoping I can somehow resolve this on a Saturday with work tomorrow at 5AM.

 

doubt there's anything you can do except buy a charger and make sure your truck has enough juice to start the next morning til you can get to the mechanic.

 

Voltmeter says a consistent (and low) reading for both baseline battery, at idle, and at 2000 RPM. Still starts fine headlights strong. Wondering if the voltage regulator is involved..

 

what's low? My alternator reports 13.7 volts almost at all times. I think I saw it above 14v for like..... 2 minutes out of the 2 years I've owned it. I have a bluetooth OBD2 scanner connecting to my phone with the torque app that shows this and other various information.

if you want, there's also a GM alternator swap. bolt pattern is very close, close enough for the swap. our alternators have 87~ amps, the GM can have as high as 140 if you go with some northstar motor alternators. you can find some threads on it here.

 

4V. Extremely low. Which is what's puzzling me because it's still operating fine except for the warning light.

 

holy shit!!!! yeah dude. your battery should be showing at least 12 volts. where are your points of contact for the test?

 

I know. I couldn't believe it, so I used a different voltmeter and replaced the batteries in the voltmeter. Same result. Standard battery terminals. Haven't gone much further than that.

 

Battery health? May have been damaged on the draw down.

 

this is what I'm thinking. either that or it's just discharged. charge it and see what happens. well, you work monday. find an autoparts store that can do some battery tests either connected or disconnected tomorrow. and see if any of them do free charges do that first. takes bout an hour.

 

Could be.. It did run pretty low when the original alternator failed. It has been running well since then and starts strong still but that's still possible. I'll have to get it tested with more sophisticated equipment than my dusty voltmeter. I wish I had one of those diagnostic scanners..

 

If your battery was really at FOUR Volts, you couldn't start the truck with it. Maybe you're not getting a good connection or maybe your voltmeter is bad. Feel free to rub those probes hard on the battery terminals to scrape though the oxidation and get a good reading.

To test your voltmeter, try measuring a known good 9 Volt battery. If you don't have one of those, a D, C, AA, or AAA battery should read 1.5 Volts.

 

See thats what I was thinking. Which is why I replaced the battery on the voltmeter and tried a different one.

But I realized a bit ago that its possible these readings are because neither of my voltmeters has an appropriate setting. There's 10 or 50, but not 20 which would be ideal. I put it on 10 and tested a 9V battery, spot on the mark. I put it back to 50 and tested a known to be working car battery, and it read 4V.

I'm now thinking (and hoping) that the sensors are throwing a false code and detecting a problem that doesn't exist, especially because the truck is still starting fine. I'm still going to get it checked tomorrow though.

 

There is no way it would only read 4 volts and have even any lights work much less start the truck. Are you using a $6 Harbor Freight meter? Don't go looking for the regulator it is in side the alternator it is what turns the light on and off and makes the alternator work. There is no way I would put a GM alternator on a Tacoma it is not plug and play the connectors will not fit and it is an inferior unit if you want more power switch to a Tacoma toy package alternator.

 

My voltmeter was certainly not $6.. when it was bought in the 80's. I had it tested by a technician. Confirmed my fears that my new alt isn't producing power. Luckily it is under warranty.

 

You put it on a known good battery and it still read 4 volts? I think it's time to go looking for a new meter.

 

In conclusion...

NAPA rebuilt alternator: Failure
NAPA warranty: Success
New Alternator: Working
Tacoma: Happy

I find it interesting that my original alt served faithfully for nearly 17 years and then the rebuild only worked for 1 month. But no matter.