Battery Light Troubleshooting Help! ('97 2.3L)

What’s going on everyone?


I’m Brody, long-time gear head. I’ve used various forums for years, been moderator on a few, and wanted to join The Ranger Station community in hopes of connecting with some Ranger experts and other enthusiasts!

I have a ’97 XLT 2.3L, 5spd, 282K.

Now I’m not a mechanic, but I’m a pretty good wrencher, okay trouble-shooter. I’ve done a lot when it comes to vehicles, a lot of experience both mechanical & electrical, but this one currently has me stumped.

The Battery Light on the dash is on, and I cannot get it to go off for shit.

To make a long story short, it did NOT come on by itself, but rather from the battery being disconnected/reconnected.

I acquired a p1443 recently, and I tackled it myself of course. Aged hose actually fell off Purge Valve Solenoid, so I replaced the hose from the Purge Valve -> Canister, as well as the purge valve solenoid itself. While doing the repair, I disconnected both negative/positive battery cables just because it’s a good idea for one, and it opened up more working space/wiggling room since the purge valve/canister setup is directly next to the battery.

The P1443 is now fixed, no more CEL, but I’ve now gained another dash-light instead, the dreaded battery light.

Now I’ve done my fair share of researching over the course of the past week that I’ve been battling it (hence the reason for the start of this thread), and I’ve done some experimenting in hopes of sourcing the cause.


First, let me start with what I do know.

I first checked voltage via voltmeter @ battery terminals a few times, coming in at around 14.60 consistently with truck on, 12.15 off. Good.

Obviously disconnected/reconnected the terminals again, numerous times. Good.

7.5a fuse #15 in-cabin good/replaced. 15a fuse Alternator System good/replaced, 20a fuse PowerPoint good/replaced under hood.

I know the battery light wire is a green/red wire, one of the 3 wires in the Alternator Wire harness. Unplugged the alternator harness, re-connected countless times. (Fluke with this is 2nd time I did this the light went off when fired up, but shortly re-appeared when started driving.) Still on.

Truck still fires right up, runs great, no changes in power from before battery light/after battery light.

The battery dash gauge is also good and reading correctly.


What I don’t know, and I’ve seen mentioned is a possible ANL mega fuse, and a fusible link.

As far as the fusible link, I saw somewhere the fusible link is grey wire coming off of starter solenoid.

Is this it?





As far as the mega fuse, I saw it mentioned being a 175amp, but I’ve done my fair share of wire tracing and I have yet to discover it. Maybe I’m wrong, but I don’t believe my truck has one in the charging setup. Really didn’t want to start going too crazy just yet though by pulling/dis-assembling the wiring harnesses, etc.

I’ve seen from multiple sources that either could be the source of my woes. But what I can’t seem to do for the life of me is find either of them.

Can anyone confirm the location, if so, and/or have pics?

Also like I mentioned, I know the battery light wire is a green/red wire, one of the 3 wires in the Alternator Wire harness. I actually found the wire right at the timing cover, and tested it. It’s only @ 1.70 volts, I’m assuming it should be reading 12v. I actually ran a jumper wire from positive+ batt terminal to the wire @ timing cover as an experiment, with the wire reading 12v with jumper wire, the battery light was still on.







This has just been an overall odd situation. Would never have expected that simply disconnecting the battery for some quick service would in turn somehow trigger the battery light indicator to come on.

Not sure what I’m missing, I am sure I’m forgetting to include something, but any insight/input would be truly appreciated, thank you!

before you go diving in overboard here... 12.15 volts is NOT a "good" battery voltage. That's about 50% of full capacity which may be OK to still start the truck but be at the threshold for the battery light to come on. Disconnecting may have simply sent it to that .01 volt it needed to come on. How old is the battery and have you load tested it?

Lol your absolutely right.

I actually meant 12.55, I don't know how I managed to typo that. Excuse me, it's past my bedtime lol.

I appreciate your response though.

I actually just went out in the cold to just check again for shits & giggles and it came in at 12.59-60.

Haven't load tested it, and the battery is a NAPA batt pushing 2 years old.

Dirtman is corect

New battery is 12.8volt
3 year old battery 12.5v
5/6 year old battery 12.3v
12.2v or under is time to shop for battery sale, next cold morning you will get "click, click, click"


The battery light circuit is pretty simple.
battery light bulb get 12v with key on, it is GROUNDED by the green wire at the alternator.
Alternator is a Ground when its not spinning, so Battery Light is on
Yes, when unplugged, you should see 12v on the green wire with key on
Unplug the green wire and Battery Light should be OFF, no Ground, if its still on then Green wire is shorted to a ground some where.

If Battery Light goes off then short is in the alternator

There is not much to charging systems so don't over do it
Stud terminal on the back of the alternator should show Battery Voltage, key off, if not big fuse or fusible link is blown
Yellow wire on 3 wire connector should also show Battery voltage, key off, if not fuse or fusible link is blown

Green wire should show 0 volts, key off, Battery voltage key on
Battery light should come on with key on
Then go off after startup
With key on unplug 3 wire connector on alternator and battery light should go off, if not green wire is shorted to ground

^Thanks for the response RonD. Appreciate the input, good info.

The battery light is off with the alternator harness unplugged.

BeeCee said:

Lol your absolutely right.

I actually meant 12.55, I don't know how I managed to typo that. Excuse me, it's past my bedtime lol.

I appreciate your response though.

I actually just went out in the cold to just check again for shits & giggles and it came in at 12.59-60.

Haven't load tested it, and the battery is a NAPA batt pushing 2 years old.

Click to expand...

Ok 12.6 is good battery then lol. You'd be suprised how many people think as long as the battery is at least 12 volts its "good" and go tearing apart things before understanding its just a bad battery.

Im not a wiring expert but Ron is, follow his steps!

Dirtman said:

Ok 12.6 is good battery then lol. You'd be suprised how many people think as long as the battery is at least 12 volts its "good" and go tearing apart things before understanding its just a bad battery.

Im not a wiring expert but Ron is, follow his steps!

Click to expand...

Lol I hear that! I use to work in a parts store when I was younger so I know how that is lol.

Still don't know how I managed to typo the most important thing lol.

Thanks again for your input tho man!

RonD said:

Dirtman is corect

New battery is 12.8volt
3 year old battery 12.5v
5/6 year old battery 12.3v
12.2v or under is time to shop for battery sale, next cold morning you will get "click, click, click"


The battery light circuit is pretty simple.
battery light bulb get 12v with key on, it is GROUNDED by the green wire at the alternator.
Alternator is a Ground when its not spinning, so Battery Light is on
Yes, when unplugged, you should see 12v on the green wire with key on
Unplug the green wire and Battery Light should be OFF, no Ground, if its still on then Green wire is shorted to a ground some where.

If Battery Light goes off then short is in the alternator

There is not much to charging systems so don't over do it
Stud terminal on the back of the alternator should show Battery Voltage, key off, if not big fuse or fusible link is blown
Yellow wire on 3 wire connector should also show Battery voltage, key off, if not fuse or fusible link is blown

Green wire should show 0 volts, key off, Battery voltage key on
Battery light should come on with key on
Then go off after startup
With key on unplug 3 wire connector on alternator and battery light should go off, if not green wire is shorted to ground

Click to expand...

I see you edited your post from what I originally saw.

I appreciate all your info!

I'm assuming the big fuse you are referring to is the one I was referring to in my original post? Can you steer me in the right direction on where it's located?

And where is the fusible link located?

Alrite, so I went out and did some testing this morning.

Battery sitting @ 12.61.

RonD said:

Stud terminal on the back of the alternator should show Battery Voltage, key off, if not big fuse or fusible link is blown

Click to expand...

Stud terminal shows 12v key off, good.

RonD said:

Yellow wire on 3 wire connector should also show Battery voltage, key off, if not fuse or fusible link is blown

Click to expand...

Yellow wire also shows 12v key off, good.

RonD said:

Green wire should show 0 volts, key off, Battery voltage key on

Click to expand...

Green wire shows 0 volts key off, 12v key on, good.

RonD said:

Battery light should come on with key on
Then go off after startup

Click to expand...

It does come on with key on, but stays on after start-up still.

RonD said:

With key on unplug 3 wire connector on alternator and battery light should go off, if not green wire is shorted to ground

Click to expand...

Like I mentioned above when the harness is unplugged, the battery light does actually go off. Comes right back on when harness is plugged back in.

Stud(B+) = Battery voltage
Yellow wire = Battery voltage
Green wire = 0v key off and Battery voltage key on

If above are true and Battery light stays on after start up then alternator is bad
In your case could just be the voltage regulator in the alternator but depending on the age of the alternator you should just swap out the whole unit.

Also if above is true then fuses and fusible links are OK, alternator is the issue

The alternator is outputting a higher voltage, 14.6v when running, which is fine just after start up.
But that voltage should drop down to under 14v after a few minutes, 13.6v is spec
I would check that, so drive it normally but don't shut it off when you get home or ??, let it idle and test battery voltage again
Should be 13.6v

If not voltage regulator is bad, for sure
Voltage regulator does a "fast charge" just after start up, usually 2volts above battery voltage, so if battery is 12.6v then with engine running it should show 14.6v just after start up
After 5 minutes or so voltage regulator will switch to "maintenance charge", usually 1volt above battery voltage, this keeps battery charged without "cooking it"

If alternator continues to output 14+volts then battery will "boil" away fluid, also hurts the plates inside.


The battery light circuit works like this:
What happens if you apply 12v to a 12v light bulb............nothing happens
You need 12v and 0v(ground), then it lights up because electrons are moving thru the filament causing it to heat up and glow.

What happens if you apply 12v and 12v to light bulb.........nothing happens
There is no flow of electrons because both sides of the filament have equal voltage.

So with key on Battery light bulb gets 12v and 0v from voltage regulator since alternator is not generating voltage, battery light bulb has electrons flowing so it lights up
At start up alternator outputs 14.6v, so battery light now has 14.6v, just like all the electrics in the truck, and it should also have 14.6v at the voltage regulator
So 14.6v and 14.6v on both contacts on the bulb, so no electrons should be flowing thru the filament so bulb is not glowing.

Battery light in most cases would flicker and come on at idle as an alternator is failing.
What happens is the alternators output drops below Battery Voltage at idle
So Battery Light bulb is getting 12.6v from battery, but at failing alternator the voltage is under that, say 10v, so electrons start to flow thru filament and Battery light bulb starts to glow.

In your case it could be the voltage regulator has a lower voltage than B+, alternators output to battery/truck, so battery light is getting 14.6v from cab fuse and then a lower voltage from voltage regulator, so lights up
This would indicate a problem in voltage regulator

Thanks a lot for the input! That makes sense.


I just let it idle for like 7 mins and the battery was still reading in the 14.60's.

I'm gonna check again later after actually taking it for a drive.


I just think it's weird disconnecting the battery would initiate this. Does that seem odd to you?

Use a sewing pin/needle to pierce the green wire while engine is running to see what voltage it has

No, not really odd

In the "old days" people would disconnect one battery cable while engine was running to check if GENERATOR was working.
This "stupid" test was carried over to alternators with external voltage regulators, these external regulators were using relays not transistors for switching so while this test could damage them it was less likely.

Internal voltage regulators are electronic, solid state, lol.
And they can become not so solid "state" with abrupt voltage changes, engine on or off.


And you should no longer Jump Start vehicles from running engine, turn engine OFF then hook up jumper cables, I would even disconnect one battery cable.
Then allow dead battery vehicle to use good battery for some extra AMPs to get it started
There will be a voltage SURGE from the dead battery vehicle when it starts, and that voltage WILL travel on the jumper cables back to the good battery vehicle, which is why you unhook one cable.
But up to you

Newer vehicles have alot of electronics now, so not really a good idea to hook them up to a "random voltage generator", which is what you are doing when you jump start another vehicle with an UNKNOWN problem, only thing you know for sure is that it's battery is dead, why it is dead could make your vehicle dead too

reading this.. Ron... could you explain "excite" pertaining to alternators? When we did the 90 amp for my boat engine I learned (and forgot) how the light relates to the excitement of an alternator. Light on to me always meant bad alt.

RonD said:

Use a sewing pin/needle to pierce the green wire while engine is running to see what voltage it has

Click to expand...

I actually have voltmeter leads that have the clamps with pin needles, and I just checked.


So first, I unplugged alternator harness and tested green/red wire @ harness pins. Green wire shows 0 volts key off, 12v key on. Looks good.

I then tested the green/red wire @ timing cover location like I mentioned in original post, picture of location below. It's @ 0v with key off. But it’s still only @ 1.70 volts with key on, although when unplugging the alternator harness the wire then turns to 12v. When alternator harness plugged back in, it immediately goes back to 1.70 volts.

RonD said:

No, not really odd

Click to expand...

IDK maybe its me lol, it just seems so weird to me to never see the light once in two years of owning it, and as soon as I unplug the battery one time the light appears, and it's definitely there to stay lol. It doesn't even flicker, that thing is on lol.

RonD said:

In the "old days" people would disconnect one battery cable while engine was running to check if GENERATOR was working.
This "stupid" test was carried over to alternators with external voltage regulators, these external regulators were using relays not transistors for switching so while this test could damage them it was less likely.

Internal voltage regulators are electronic, solid state, lol.
And they can become not so solid "state" with abrupt voltage changes, engine on or off.


And you should no longer Jump Start vehicles from running engine, turn engine OFF then hook up jumper cables, I would even disconnect one battery cable.
Then allow dead battery vehicle to use good battery for some extra AMPs to get it started
There will be a voltage SURGE from the dead battery vehicle when it starts, and that voltage WILL travel on the jumper cables back to the good battery vehicle, which is why you unhook one cable.
But up to you

Newer vehicles have alot of electronics now, so not really a good idea to hook them up to a "random voltage generator", which is what you are doing when you jump start another vehicle with an UNKNOWN problem, only thing you know for sure is that it's battery is dead, why it is dead could make your vehicle dead too

Click to expand...

Very insightful! And agreed!

I don't think I ever tested the green wire when it was plugged in, but it does power the Rotor in the alternator for start up so I can see it dropping down in voltage because applying voltage to rotor should cause alternator to spin, but of course it can't because of fan belt, lol.
Alternator is "kind of" like an electric motor in that respect, you apply voltage to brushes on the rotor and electric motor spins

An alternator can't just generate voltage by spinning it, it must have "start up voltage" applied to rotor to generate the magnetic field that causes the 3 Fields in the alternator's case to produce their AC Volts.

Thats what the green wire is for, it supplies the "start up voltage" and is also the ON/OFF switch for alternator.
As said above alternator is like an electric motor, if you didn't cut power to the rotor with key off, alternator would drain battery pretty fast trying to turn the engine via the fan belt

Once the alternator starts to generate its own voltage then green wire is just for Battery Light circuit, it should have same voltage as battery positive or B+ when engine is running, if not then battery light would be on, and something is wrong inside voltage regulator, assuming green wire checked out OK


One wire alternators use an RPM switch inside as the "green wire"
These alternators just have the B+ connection(stud) on the back, connected to battery positive with a fuse or fusible links

Inside there is an RPM(centrifugal) switch with a connection to internal voltage regulator and B+
When alternators RPMs get above, say 1,200(alternator RPMs not Engine RPMs), then switch closes and 12v is sent to voltage regulator and the rotor, which starts alternator generating its own voltage
When engine is shut off and RPMs drop then switch opens and alternator won't drain battery

Denisefwd93 said:

reading this.. Ron... could you explain "excite" pertaining to alternators? When we did the 90 amp for my boat engine I learned (and forgot) how the light relates to the excitement of an alternator. Light on to me always meant bad alt.

Click to expand...

Denise,

It takes 3 things to generate a voltage. A coil of wire, a magnetic field and relative motion between the coil and field. The armature, or rotating part of an alternator or generator is where the magnetic field is. The stator is the coil(s) of wire where the voltage will be generated. So, since the armature is just coils of wire on a rotating shaft, we must apply voltage to those coils to produce the magnetic field. Applying this voltage is called "exciting the field". Varying the voltage to the armature field windings changes the strength of the magnetic field, thus changing the voltage that is produced in the stator coils which is then rectified to make it DC for your vehicles electrical system.

This message composed solely of recycled electrons. Go green!