I’m new to the forum after having read a few threads on the same issue from other year trucks and I’m hoping someone can help with mine. I’ve got a 2000 Ranger XLT with a 4.0, 4x4, and manual transmission. It has the extended cab, long bed and 170,000 miles. My battery light came on while I was driving and the truck died not too long after. I was towing my camper out to my land at the time and it was late at night so I put the spare camper battery in my passenger seat and ran jumper cables to the engine bay and drove the last few miles that way. I got a ride back into town and let my truck stay out with the camper until recently when I brought my camper back into town to sell it. I took a new battery out with me, installed it and drove back into town (my dad’s truck was hauling my camper). I figured my alternator had gone out so I put the trickle charger on overnight and a couple days ago I picked up a new alternator (upgraded the 95amp to a 130amp) and installed it.

The battery light went out and it seemed to run fine but the voltage seemed low. The next day the truck died again on my way home. I got someone to come out and I hooked up jumper cables, let it charge for a few minutes, then connected the one jumper cable from the positive post on the back of the alternator directly to the positive battery terminal and it ran just fine all the way home with the voltage meter reading where it normally does, about half way up. I took the truck to O’Reilly’s this morning and had them hook up their electrical testing machine and it showed the alternator had failed and they said it was the voltage regulator and to replace the alternator.

I took the alternator back to the Napa I got it from and they bench tested it there and it wasn’t putting out any voltage so they exchanged it for another. I had them test the second new one before I left the store and it was working properly. I brought it back home and installed it, then put the battery back on the charger to top it back off. I drove it to a meeting tonight and now the dash battery light is on and the voltage is showing lower than normal, like it has been lately. I’ve checked all the fuses, in the cab and under the hood in the top driver’s side corner and they’re all fine.

I can’t figure out for the life of me what’s going on and how to fix it. I’m great with mechanical fixes but electrical issues have never been my strong point and this is no exception. I understand the theory and can wire things well enough but troubleshooting existing wiring is somewhat frustrating. I love my truck and want to fix it but this ongoing issue this past week has me wanting to look at just buying something else. I can’t see myself actually getting rid of my ranger but that’s my current level of frustration with this. I can’t find any fusible links or anything that looks or seems like it would explain the issue. It seems like it should be straight forward and simple but my frustration seems to be clouding my thinking. Any help anyone can offer would her VERY much appreciated! Thanks!

 

Welcome to the forum

You need to get a Volt meter, $10-$15, test light won't work for this

A car battery is only use to start the engine, the alternator provides ALL the voltage/amps for the whole vehicle when engine is running
A car battery will have 12.8volts to 13.0volts when brand new, this is important since it will lose about 0.1 volt a year, and when it gets down to 12.2volts is done, needs to be replaced, so you get about 5 years from a car battery, maybe 7 years from a good one, miles don't matter, startups don't matter its a TIME thing

So a working battery will show 12.3v to 12.8v over its life, and you can only test this AFTER battery has been sitting(NO CHARGING) for 4 hours or more, more is better

Alternators are pretty simple, but can NOT be bench tested, well they can be tested as bad but can not be tested as good, that can only be done in a vehicle, just FYI
2G and up Alternators have 3 "working wires"
B+ wire is the larger one on the stud/nut connection
Then a 2 or 3 wire connector for the internal voltage regulator, the Yellow wire and the Green wires are the ones you test

Key off
Set volt meter to 20vDC, or just DC Volts
Test battery voltage and remember it or write it down

Put/hold Black Volt meter probe on alternator's Metal Case, that's the Ground, it is hooked to the Battery Negative terminal, via it's cable to engine block
Put Red Probe on B+ terminal(wire stays connected), should see Battery volts EXACTLY..................exactly, if not thats an issue

Unplug the 2 or 3 wire connector on alternator
Test the Yellow wire, should see Battery volts, exactly, if not thats a problem

Test Green wire, should see 0 volts, or barely any volts
Turn key ON
Re-Test Green wire, should now see over 12volts, slightly less than Battery Volts is OK since key is on
This Green wire is the ON/OFF switch for alternator, its also the Battery Light wire
Battery light comes on with Key on but engine is off, because the light bulb gets 12volts and alternator is 0volts, because it is not spinning/generating volts
If alternator stops generating volts while spinning the Battery Light comes on for that reason, alternator's Green wire connection is 0 volts

If these 3 wires Test as OK, then the vehicles system is OK, 100%, no if, ands, or buts
So very very simple to test the vehicle wiring and fuses

Hook 2 or 3 wire connector back up
Start engine
Test Battery Volts, should see above 14 volts(thats alternator voltage), but under 15volts, over 15volts is ALSO a bad alternator, just FYI
After engine has been running for about 5 min, battery voltage should be under 14volts, 13.5v to 13.9v is spec, but never under 13.5volts
If its under 13.5volts alternator is bad, assuming wire tests were good, thats for sure bad, doesn't matter if bench test showed "good" its a false good

I have read of people going thru 3 or 4 alternators of the same brand to get a good one, so just FYI, these are not tested when they are made, just boxed and shipped, YOU are the tester, so keep the recepts


A bad/failing battery can kill an alternator
A bad/failing alternator can kill a battery

So its not unusual to have to replace BOTH battery and alternator at the same time or within a few weeks of each other

 

Thanks so much for the response. I’ve got a multimeter and will run the tests you suggested later this evening and report the results back. I did replace the battery AND the alternator within a couple days of each other and I’m now on the second alternator. Again, thanks for your reply and advice. I’ll let you know what the readings are as soon as I have them

 

So it’s as I was kind of expecting… I connected my multimeter to the B+ terminal and the ground and it gets NO voltage at all. Nothing. I’m tracing the wire back and it goes down to the starter.

 

On a 2000 Ranger the B+ wire should go to the 175amp Mega Fuse on the outside of the engine fuse box

Check that the Mega fuse has 12v on BOTH terminals, if only 1 has 12v then its blown, if no 12volts on either then wire to battery positive terminal is bad

Diagram below

 

I traced it back and found the piece you are referring to just before I checked my phone and saw your reply. I’ve looked at that thing countless times and didn’t realize it was even there. I’m trying to find a new one now.

 

The one that was in there was rated at 125amps which was fine with the 95amp alternator but with the larger 130amp alternator, which tested at 139amps, 125 wasn’t going to cut it. Im on my way to go pick up a 175 now. Thanks for the help! I’ll let ya know if this solves it

 

Yes, the 130amp alternator may have blown the 125 amp fuse, but you would have had to pull alot of amps thru that fuse

Stock vehicle with engine running and all electrics on, i.e. headlights and fan on High, would draw may be 60amps

130amp alternator doesn't send out 130amps, it can send out up to a 130amps, but it only sends out the amps the system needs at that time

 

I see. Maybe it was already bad then and that’s what killed the first battery back when I was hauling my camper.

Either way thank you soooo much for the help! I can’t even begin to tell you how much I appreciate it. I can’t believe I overlooked the fuse right in front of my face. I tore all the wire looms apart looking for a bad wire or a fusible link and looked at that fuse countless times and never realized it was even a fuse. I feel kind of dumb but mostly just super grateful to have it fixed!

 

Thanks for the thanks but don't be too hard on yourself

I have spent hours on No Starts when the vehicle was OUT OF GAS
You would think after the FIRST ONE you would learn, check if there is gas in the tank, but NO, its happened to me 3 times, well 4 to be honest but caught that in the first 15min, lol