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Battery Light on still have 14.5 volts

77K views 9 replies 7 participants last post by  jwchurch 
#1 ·
Anyone know how the battery light is triggered, I have the light on the dash but voltage is 14.5 at the batteries with the engine running.
 
#2 ·
There is a single wire circuit, it is a single pin connector on the alternator. The connector on the alternator or the connector on the wire itself can be fubar. Just because it is putting out 14.5 V doesnt mean it is putting out the right amperage, either. Wiggle that single pin wire and see if the light goes on and off. If that doesnt work, have the alternator load tested and diodes checked.

Just curious, does that meter you have read AC voltage? If so, measure the AC ripple at the battery. It should be less than 0.1 V.
 
#3 ·
Only one 2 pin connector on the alternator, and on AC I read 0.3 to 0.1. I was curious if the PCM sets the light and how it determines to do so since there wasn't a single indicator wire like I am used too. Are one of the wires on the 2 pin plug for that, I thought one was a ground and one positive.

Thanks for the help.
 
#4 ·
Like Matthew said....

It's a single wire from the alternator (in the 2-wire plastic connector) that goes DIRECTLY to the back of the cluster.

With the engine running, disconnect the 2-wire connector (please be careful). If the battery indicator goes out, it's the regulator grounding the indicator circuit....

See this thread...I posted some pictures of the charging circuit:

http://www.ford-trucks.com/forums/783731-chargin-system-light-goes-on-and-off-randomly.html
 
#10 ·
So I changed out my glow plugs, valve cover harnesses too. After putting it all back together, Battery light is on? Read your post, unplugged pigtail, light went out. Wire kinda loose on plug so bought a new one. Same problem, battery light still on. #6 fuse replaced, batteries and alt check ok? Alt new last year.

What did I leave unplugged?

Need help, THANKS!

Jeff 99 F250 7.3 SD
 
#6 ·
There is a fuse that can blow and make the Batt light stay on. I cant recall which one it is now but mine did it.
 
#9 ·
:whs:unpluging the connector will make the light come on you should have at least the batt voltage to both the small wires... with the engine running 13-15 volts i think there are also two ...5a fuses there they are for dual alts but are still wired there for some odd reason had one 5a through me for a loop.
 
#8 ·
man i bet the alternator just isnt putting out the correct amperage... does the light stay on all the time or is it intermittent? mine would always come on when i first started and go off till i started driving...

and i belive this is because the GP circuit was taking up the amperage and the batteries would then fall below the 12v. or whatever sets off the light. the alternator would put out enough power to run the truck and keep the batteries charging but not enough to actually charge them.

Also when i towed a trailer with brakes when i hit the brakes the draw from the trailer would almost kill my truck. so just because you have 14.5 at idle under no load doesnt mean the alternator is good.

mine gave 14.5 every time i checked it light on or off. couldnt really check it under load...

so id get the alternator load tested and id bet youre more than likely gonna have to replace it. just be happy its giving you a warning and not just going out randomly when youre in the middle of a 1200 mile roadtrip with the kids in the back and ma in the right seat.
 
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