‘94 RRC LWB battery light

Blueboy

Well-known member
Apr 20, 2004
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Back in the USA; Rockwood, PA
Don’t usually drive the Rangie at night yet recently noticed with the headlights on when I brake the battery light dimly lights. As soon as the brake pedal released the light goes out. Only happens when headlights on.

What do you think? Where should I start?

Thanks.
 

Flyfish

Well-known member
Oct 29, 2004
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St. Louis
New alternator within 5 months. 13.1 volts. Looked at my records and realized the battery is almost 7 years old. Time flies. Probably due to change out.

Thanks!!
13.1 seems a little low. But take a reading on the battery after it’s sat overnight or whatever without being charged. And just double check the connections on the alternator too.
 
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Flyfish

Well-known member
Oct 29, 2004
1,402
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St. Louis
Couple other things to check/verify…..

I assume the 13.1v reading is at idle. See how high the voltage goes when you pull on the throttle cable and rev the engine a little. If it doesn’t change much, there may be something wrong with the alternator.

I would also check the voltage readings again at idle with the headlights on. Maybe there is a short or bad connector that’s drawing excess voltage when you turn the lights on. And then maybe watch the voltage while someone hits the brake pedal.
 
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discostew

Well-known member
Sep 14, 2010
7,706
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Northern Illinois
New alternator within 5 months. 13.1 volts. Looked at my records and realized the battery is almost 7 years old. Time flies. Probably due to change out.

Thanks!!
Make sure the belts are tight. It's kind of a goofy setup. Check that your grounds are good and tight. I don't think a battery will cause this. once the truck is running that battery is just along for the ride. A capacitor more or less.
What happens to that 13.1 volts when it's idling with the brake lights and headlights on. I bet it drops.
 
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Blueboy

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Apr 20, 2004
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Back in the USA; Rockwood, PA
Couple other things to check/verify…..

I assume the 13.1v reading is at idle. See how high the voltage goes when you pull on the throttle cable and rev the engine a little. If it doesn’t change much, there may be something wrong with the alternator.

I would also check the voltage readings again at idle with the headlights on. Maybe there is a short or bad connector that’s drawing excess voltage when you turn the lights on. And then maybe watch the voltage while someone hits the brake pedal.
Yes at idle. Will give that a shot as well. And hope not the alternator

Also good suggestions. Appreciate it.

Hate electrical shit.
 
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Blueboy

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Apr 20, 2004
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459
Back in the USA; Rockwood, PA
Make sure the belts are tight. It's kind of a goofy setup. Check that your grounds are good and tight. I don't think a battery will cause this. once the truck is running that battery is just along for the ride. A capacitor more or less.
What happens to that 13.1 volts when it's idling with the brake lights and headlights on. I bet it drops.
Yes, the belt tensioning was a pita.
Where are the freaking grounds on a RRC??
Will check that as well. Thx.
 

Blueboy

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Apr 20, 2004
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Back in the USA; Rockwood, PA
And when lit…..what? I think you left something out.

I do that all the time using talk to text..
I do it all the time due to oldness!

Earlier this year I could have the high beams and the Hellas and brake without any issues. It is only recently that the battery light is dimly illuminating with just the low beams.
 

discostew

Well-known member
Sep 14, 2010
7,706
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Northern Illinois
Yes, the belt tensioning was a pita.
Where are the freaking grounds on a RRC??
Will check that as well. Thx.
I'm just talking about the main ground cables and main body ground. You don't have to find them, you can just look for any voltage drop in the ground side with a meter. Let it idle with all the loads on, use a short stick between the seat and the brake pedal to hold that on. Then just measure the differance of potential between the battery neg post and the engine block, the alternator case, the body. Your looking for anything getting close to a half volt.
 

Blueboy

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Apr 20, 2004
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Back in the USA; Rockwood, PA
I'm just talking about the main ground cables and main body ground. You don't have to find them, you can just look for any voltage drop in the ground side with a meter. Let it idle with all the loads on, use a short stick between the seat and the brake pedal to hold that on. Then just measure the differance of potential between the battery neg post and the engine block, the alternator case, the body. Your looking for anything getting close to a half volt.
As always thx for the advice. Will check it out.
 

Blueboy

Well-known member
Apr 20, 2004
3,205
459
Back in the USA; Rockwood, PA
I am right there with ya!

At least checking voltage is easy. And that should give us some direction or at least rule things out that test normal.
Ok, checked after run up to local ski area.

At idle voltage is 13.1 volts no load
At 2k rpm 13.4 volts no load
At idle voltage is 13.1 volts with headlights on high beam
At 2k rpm voltage is 13.3 volts with headlights on high beam
At idle voltage is 13.1 volts with headlights on high beam and brake pedal depressed
At 2k rpm voltage is 13.3 volts with headlights on high beam and brake pedal depressed.

No battery light.

Drove the beast 10 miles up to ski area today as nice day and no salt. When I left battery light dimly left when braking. No headlights on. Half way through trip light off when braking. On way back turned on headlights high beam and braked coming down hill. No battery light.

Did it just needed driven? Are the Rover gods helping?? Thx for your help.
 
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mgreenspan

Well-known member
Feb 28, 2005
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130
Briggs's Back Yard
Could it just be a bum wire somewhere in your elec system? Like a battery grounding cable or an alternator cable to the battery that is loose or corroded a bit?