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Battery light on, batteries and alternator good

74K views 17 replies 12 participants last post by  Absolute 
#1 ·
Hey guys-

When it rains, it pours. Just about to take my truck in for a bunch of odds and ends getting repaired, and the battery light is now on most of the time when I'm not on the gas pedal. Probably about 60% of the time today.

Had the batteries and alternator checked once off the truck, and twice on the truck, tested good. Cleaned all my battery posts, and the ground straps. I'm going to check tomorrow for loose connections, but what else should I be looking at?

The truck starts fine, batteries read great, no power loss. I'm friggin stumped.

I did have a CEL on for problem with the EBPV sensor circuit. I have noticed that after replacing the tube (was broken in half) and the sensor, the EBPV doesn't seem to hold when warming up. It sort of closes, so I hear the whoosh, and then there's a small squeak and it stops, and then it repeats over and over. Any relation?
 
#2 ·
You need to stop trusting those free checks and get you a volt meter gauge so you can watch what's going on. Wally world has a nice one that plugs into your cigarette lighter that works very well. Made by innova and it matches readings on my AE.

I had a similar issue with an Autozoo alternator the last time I swapped it out. Light started coming back on within a couple of days. Voltage was fair. The alternator was charging and not dropping too low, but it wasn't putting out the 14+ volts I like to see while running. Had that tested at Autozoo 4 times and it kept passing. I finally told them I wanted a new one since the voltage was a tad low and I didn't want my dash light to keep coming on. They agreed and the one I have now charges at 14.2 so me and my dash light are happy again.
 
#3 · (Edited)
I do have a multi meter that allows me to check voltage. I'll hook that up tomorrow and see what it says. The battery light hasn't gone on as constantly until today, so I'll check it tomorrow. Hopefully that's all it is...

I do know it was reading about 14.2 at the batteries when I checked it last time, but the battery light was never on, or lfickering, when I ran those tests...
 
#4 ·
Just an update : I did get NAPA to replace my alternator. My truck is @ the mechanics now for other issues, so he's gonna swap them out, and hopefully that cures this problem. I'll post back after I get the truck back.
 
#5 ·
hope it fixes your issue. I have read that even though you get a new alternator; there are known issues with some that cause this problem with the battery light.
 
#7 ·
Yea, I had them tested off the truck separately first.

INFRNL - Do you mean issues with the alternators, or with the truck?
 
#8 ·
ditroidfd, Look under the hood @ the main fuse panel by the Brake Booster. There are 2 fuses, I forget the number, should be in your Owners Manual. They have something to do with the Field Current from your Alternators. One or Both may be blown.
I had this happen to my old Ford & after I changed the Alternator the light would still not go out until I replaced the fuses. hope this helps. :read:
 
#13 ·
Fuse number 6 and 7, a 5 amp and a 10 amp. I am having similar issues and will be taking a look at mine tomorrow
 
#10 ·
Reg, I'll check that too, thanks!
 
#11 ·
an you tell me what you found? I am having a very similar problem.

Thanks

I have a 2001 Ford Excursion with a 7.3L diesel with an alternator (charging system light) that doesn’t seem to make sense.

As of today, I have two good batteries, tested and verified with a Midtronic POWER LOGIC. They are both motor craft batteries only 2.5 years old. About 2 weeks ago, my alternator died and I had it tested and the regulator was replaced. It was bench tested to verify the fix and I re-installed it. I also have the Midtronic handheld system analyzer. Which I used to verify the function of the newly repaired alternator. The tester indicated the diode ripple is good and the charging system is normal.

Alternatively, I have put a meter on the batteries (both independently) and found the voltage to b e14.2 or so when there are no loads applied. When loads are applied, the voltage is 13.6 or so.

Seems like the system is working fine but the light is still on.

I have also verified I have 12Volts present at the orange and blue wire at the two wire alternator connector.

Any ideas what to check next?

Thanks in advance for any help you can offer.
 
#12 ·
The circuit that controls the light is in the alternator itself. I had a rebuilt alt the worked well producing a good 14.5v, however, the light would not extinguish. Replaced the alternator and all was good.
 
#16 ·
FWIW, several years ago, I had similar issues. I changed out the alternator and put new batteries in, and I'd still see the occasional ghost battery light coming on. The cables looked ok on the ends, but, I slit the cable going to the starter back about a foot from the battery, and the wire was eaten up inside with rot. I had a similar problem in a Nissan pickup 20 years ago, so I should've hit on the cable issue sooner. Anyway, I went ahead and put on a new complete wire loop, and any charging issues and the ghost light issue that I had went away. Its been fine ever since.

just my .02 cents worth

short_stuff
 
#18 ·
I recently had this battery light issue. I have DP Tuner dash controller so I can see my voltage all the time. My light started coming on when I was on the pedal, then it progressed to on all the time. My voltage never showed more than 14.3 volts, and glow plugs on only dropped to about 12.5 volts. So it was fine. Real odd. Then it happened. Driving along and my dash goes black, all the gauges drop off dead, stereo shuts down, then all fires back up, driving along motor never skips a beat. Then it does it again. Voltage still never moved. So did a data log for half hour. It reset my dash 4 times in that time, and was obviously progressing worse. Went over the data log, and there it was!! For not even a whole second, the voltage spikes to 16.8 volts, makes the dash area fail, then drops back to normal. It is the alternator. Took it back to Napa on life time warranty, New one immediately fixed issue. No more light, no more dash failures. First time ever I had an alternator fail, that was charging too much!
 
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