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post #1 of 10 (permalink) Old 12-30-2010, 04:33 PM Thread Starter
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Battery light

What exactly does the battery light on the Ranger indicate?

On Christmas day I had real problems with the electrical system. Barely made it to my sister's and toasted the battery in the process. Battery now reads 3V and putting it on a trickle charger made no difference. Never once did the battery light come on.

Replaced the battery and drove home. A couple of times the battery light flickered very lightly... but nothing more than a flickering and not for long. I doubt it was flickering for all of 10 seconds total over a 45 minute trip.

The voltage gauge on the other hand seems to work. On the trip there it went lower and lower. Really became a problem when the needle dropped below the normal range. On the way back it stayed in the lower end of the normal range.

Replaced the battery, alternator, and fan belt. The old alternator makes a clicking noise when you spin it.

The battery now reads 12.95 disconnected and 15.2 under low idle load. Seems a bit high to me, but the difference is less than 2.5 volts so it isn't overcharging?

I also had to disconnect the DRL module since it wasn't working and was causing the high beams to come on when I turned off the truck. Could it have not liked the low voltage?

So everything seems to be working fine. Truck runs great again. Voltage reads correctly. Everything else seems normal.

But now the battery light goes on and off at random intervals. I can start the truck and pull the +ve cable from the battery and the truck keeps running fine.

Any ideas? The battery light didn't come on when the alternator toasted. Didn't come on when the battery was basically dead. Never came on before this problem. And now comes on with a new battery and alternator.
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post #2 of 10 (permalink) Old 12-30-2010, 05:18 PM
 
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How old is your truck? Sounds like you might have a bad connection somewhere. Time and weather take a toll.

I'd start by pulling off all the ground cables at the engine, chassis, battery, alternator and cleaning them up really well with sandpaper and a wire brush. Then coat them with silicone grease to protect them from oxidizing.

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post #3 of 10 (permalink) Old 12-30-2010, 07:11 PM Thread Starter
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Truck is a '98, so not that old :D

I will look into the grounds. I was surprised at how small the ground wire from the battery negative to chassis was. I remember them being larger on older vehicles.

Also, the ground strap at the back of the engine bay seemed brittle to me. This is the exposed woven strap.

But what does the battery light show? It can't just be voltage since there is already a voltage gauge?
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post #4 of 10 (permalink) Old 12-31-2010, 02:42 PM
 
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The alternator light is just a simple circuit connected directly to the alternator. For the battery to charge, it must have a higher voltage connected for current to flow through it (which gives the charging action).

The alternator light is isolated from the rest of the vehicle (battery) circuit by a diode. If the voltage from the alternator circuit is lower than the battery circuit, then the light turns on. That indicates the alternator is not producing sufficient voltage to charge the battery.

The voltage meter basically indicates the battery voltage, whereas the alternator light gives a simple indication of the alternator voltage. Usually, you don't need to know the exact voltage produced by the alternator -- you just need to know that it's a little bit more than the battery voltage. That's why it's just a light.

From what you've said, the battery seems to be charging alright -- the voltage with the alternator connected to the battery is 15.2V, and lower when not running, 12.95V.

Don't know exactly what the alternator harness looks like on a '98, but there should be a seperate alternator light wire -- smaller gage -- that goes directly to the voltage regulator inside the alternator. In my '07, it's gray. Your's might be a different colour. Check that wire and it's connector. Maybe it got damaged installing the new alternator.

What kind of alternator did you put in? Is it a new one? If it's remanufactured, the voltage regulator could be borderline. The voltage regulator module provides the alternator light signal. Does the voltage you measure with your voltmeter vary significantly as you rev the engine? It shouldn't.

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post #5 of 10 (permalink) Old 12-31-2010, 03:14 PM
 
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you may just have a bad rebuild if the batt light concerns are after replacement,should have warranty,also check the ground stud on the front of engine and the fender clamp for corrosion.


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post #6 of 10 (permalink) Old 12-31-2010, 04:10 PM Thread Starter
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Originally Posted by b4000 View Post
Don't know exactly what the alternator harness looks like on a '98, but there should be a seperate alternator light wire -- smaller gage -- that goes directly to the voltage regulator inside the alternator. In my '07, it's gray. Your's might be a different colour. Check that wire and it's connector. Maybe it got damaged installing the new alternator.

<clip>
Thanks for the description. That makes sense. It is really an alternator light, it is just shaped like a battery so it is clear

When I was first looking at the problem I noticed the connection for the single wire was very corroded. It isn't sealed as well as the other connectors. Really, I am surprised it worked, but it was probably corroded in place.

I sanded the connector and we will see if the light comes back on. My wife has been using the truck all afternoon, so I can't check.
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post #7 of 10 (permalink) Old 12-31-2010, 08:46 PM Thread Starter
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Update: Looks like the connector was the cause of the battery light problem!
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post #8 of 10 (permalink) Old 12-31-2010, 08:57 PM
 
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Great news..thanx for the update. It may help someone else too.

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post #9 of 10 (permalink) Old 12-31-2010, 11:02 PM
 
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Great news..thanx for the update. It may help someone else too.
Agreed. Always good to know what the solution to these problems turns out to be.

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post #10 of 10 (permalink) Old 01-01-2011, 03:09 PM
 
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Quote:
Originally Posted by seanm View Post
What exactly does the battery light on the Ranger indicate?

On Christmas day I had real problems with the electrical system. Barely made it to my sister's and toasted the battery in the process. Battery now reads 3V and putting it on a trickle charger made no difference. Never once did the battery light come on.

Replaced the battery and drove home. A couple of times the battery light flickered very lightly... but nothing more than a flickering and not for long. I doubt it was flickering for all of 10 seconds total over a 45 minute trip.

The voltage gauge on the other hand seems to work. On the trip there it went lower and lower. Really became a problem when the needle dropped below the normal range. On the way back it stayed in the lower end of the normal range.

Replaced the battery, alternator, and fan belt. The old alternator makes a clicking noise when you spin it.

The battery now reads 12.95 disconnected and 15.2 under low idle load. Seems a bit high to me, but the difference is less than 2.5 volts so it isn't overcharging?

I also had to disconnect the DRL module since it wasn't working and was causing the high beams to come on when I turned off the truck. Could it have not liked the low voltage?

So everything seems to be working fine. Truck runs great again. Voltage reads correctly. Everything else seems normal.

But now the battery light goes on and off at random intervals. I can start the truck and pull the +ve cable from the battery and the truck keeps running fine.

Any ideas? The battery light didn't come on when the alternator toasted. Didn't come on when the battery was basically dead. Never came on before this problem. And now comes on with a new battery and alternator.
take a mulit meter and check voltage from alternator + to battery - if its below ~13.7 then thats probably why its on and you have a charging issue. if you have above that then voltage drop alt + to batt +. should be below ~150mV (0.15V) any more and you have bad resistance somewere. if all thats good check the wiring to the battery light, it could have resistance too causing it to see less that it should.

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