Battery Light?

imelmo · Apr 14, 2013

The battery light has been on for the past few days while the truck is running. I checked the battery connections and connections at the alternator and they're all good. CTS shows 13.8V-14.0V while running. With the truck off it reads about 11.8V. I'm going to put a meter on it tomorrow just to double-check but the truck runs fine and there aren't any cranking issues.

What else could be making the light come on?

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Atsah · Apr 14, 2013

11.8 is a little low.. put a meter across the battery engine off and headlights on, wait a few minutes before you check it (check both).. All my trucks sat at 14.6 idleing and 12.5 off..

imelmo · Apr 14, 2013

I know it's a little low but would 13.8V while running be enough to set the light off?

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Dzchey21 · Apr 14, 2013

No it shouldn't do that.. Something isn't right

Atsah · Apr 14, 2013

imelmo said:
I know it's a little low but would 13.8V while running be enough to set the light off?

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I would say no.. Check all your grounds.. The light stays on all the time?

imelmo · Apr 14, 2013

Yup.

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DEEZUZ · Apr 14, 2013

connector pins are maybe spread. have someone wiggle the connector on alternator and watch if the light coincides with movement

imelmo · Apr 15, 2013

Put my meter on it and the batteries are at 12.77V with the truck off, 14+V running. Gotta be a ground I guess?

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Atsah · Apr 15, 2013

imelmo said:
Put my meter on it and the batteries are at 12.77V with the truck off, 14+V running. Gotta be a ground I guess?

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Ya, the numbers are right..

jngreen · Apr 15, 2013

On my old truck, a 7.3, my light would come on and all I had to do was wiggle the wire and connector on the alternator, and the light would go off.

Snake · Apr 15, 2013

Danny, I don't have the schematic in front of me, but its possible for the light to be there even if everything is working properly (alternator and batteries). I'll have to go back through some of my old posts to see if I can find anything worthwhile.

Scott@All Pro Diesel · Apr 15, 2013

Alternator is going out.

Snake · Apr 15, 2013

Scott@All Pro Diesel said:
Alternator is going out.

Yeah? His alternator is putting out 13.8-14.0v at idle. What should he see?

Danny - just read through these posts again. The 11.8v you see with the truck off....is that KOEO?

Scott@All Pro Diesel · Apr 15, 2013

It is an internal failure of the alternator. The light comes on because the computer is seeing a voltage drop from the alternator. I have seen the alternator last months or days, even though you can not see a problem with a volt meter, the alternator will eventually give out. The 11.8 volt that he sees when the key is on is probably the glow plugs cycling. Need to check voltage after glow plugs have cycled. Battery voltage, with key off, should be around 12.4.

imelmo · Apr 15, 2013

Snake said:
Yeah? His alternator is putting out 13.8-14.0v at idle. What should he see?

Danny - just read through these posts again. The 11.8v you see with the truck off....is that KOEO?

I got those numbers off my CTS. It appears to read a little lower than actual. The meter showed 12.7V with keys out, 14+ with the truck running.

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Snake · Apr 15, 2013

Completely agree with the CTS reading a little lower than actual. I've heard the same thing from pretty much everyone who has a monitor plugged into the OBD port (myself included).

Just to make sure I understand, you're seeing ~ 11.7v KOEO, 12.7v engine off (nothing on), and 14v at idle?

Doing some more digging on my side. I had alternator problems last year and someone explained how your situation could pop up. I can't remember if it was on here, the org, or PSN....

Edit - check out post #26

http://powerstrokearmy.com/forums/showthread.php?t=19277

imelmo · May 12, 2013

The battery light is just as bright as the other lights, brighter in my eyes actually. LOL

Anyone else have any ideas? I double checked all the grounds I could think of and couldn't find anything unusual. Batteries and alternator are doing what they're supposed to.

Passenger side battery:

Driver's side battery:

Alternator:

The battery checks were done after the truck sat overnight and hadn't been started. After I started the truck, the passenger side was 14.4V and the driver's side was 14.36V.

Someone told me they had a similar issue and it was whatever this thing is on the alternator harness. Supposed to be a fuse or something like that:

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TERRCO · May 12, 2013

I re-read all the post and unless I missed it I didn't see if you disconnected the battery terminals to check voltage on each battery. You need to check each battery separate. Voltage will be the same on both batteries unless you disconnect the cables. Just because it starts fine doesn't mean one of the batteries could not have a problem.

imelmo · May 12, 2013

TERRCO said:
I re-read all the post and unless I missed it I didn't see if you disconnected the battery terminals to check voltage on each battery. You need to check each battery separate. Voltage will be the same on both batteries unless you disconnect the cables. Just because it starts fine doesn't mean one of the batteries could not have a problem.

Hmmm, ok. I'll check that next.

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hawgdoctor · May 12, 2013

Normally if you see that light if means the regulator inside the alt is on its way out. Seen em last week, and seen em last several moths like that. Check with one of the local parts houses, and see if the can test it. If its back feeding the light circuit be ready for a new one Danny.

sent from the shop making things fly.....