Had a bad alternator, changed it, and now the battery lite stays on all the time..Changed the alternator again with a known good one, and the light is still on all the time..would anyone here know the problem?

 

I hope so, but it ain't me. Both times I've had this problem a new alternator solved the problem. But you can bet someone here will pop in soon, so just kick back and relax. By the way, welcome to FTE!

 

What is your voltage while running? (should be around 14.4 volts). I would check your wiring real close.. I had a battery light on and the cause was one of the two wires that come off the top of the alternator was rubbing on the alternator aluminum housing, down from the connector about 1 & 1/2 inches.. Had to use a magiflyer glass to see the bare copper wire showing thru.. Bent back the wires and added some insulation .. good ever since..
Another area to check is the main wire harness that goes over the top of the driver's side valve cover.. read posts where the harness rubs on the cover.. (your altenator wire is inside this harness i believe..)

 

My Expo had the same wire rubbed thru and it had blew a fuse labled ALT it was a 10 amp. I fixed the wire and replaced the fuse and the light went out

 

You need to check both of your batteries. One of them may be bad and causing the light to stay on.

 

Checked both batteries..12.4 v at each...visual on all wiring, still no problem found there...Where is this 10A fuse someone is talking about..cant find it w..which fuse box..under hood, or in cab....

peter

F250 SD 1999 Diesel

 

Battery junction box mega fuse
Battery junction box (BJB) fuse:
6 (10A)
7 (5A)
Central junction box (CJB) fuse:
29 (5A)
Charging system warning indicator
Circuitry
Cables

.
Sorry no pictures.

 

where are BJB and CJB Located?
Peter

 

I don't know the location. But I would take a guess at a blown fusable link.
If it were my truck I would start tracing the wiring harness and looking for that.
And checking EVERY fuse on both of the boxes.

 

checked all the fuses with tester..all are fine..no chafed wires...Surely am stumped now!
Peter

 

#6 Single or dual alt "A" field, regulator.

 

Did you check them unhooked, if not, you could be reading only the good battery.

 

yes, they were both unhooked at the time...checked them again as well ad they are 12.3 each..Also double checked fuse #6 under the hood, and it is fine..Are there any fusible links that I might be checkin?? This is a mystery..

 

Time to check the voltage while running like Clint suggested above. If you are not getting over 14 volts, then something is unhooked or you have another bad alternator. Yes they can be bad out of the box. Certainly wouldn't be the first around here.

 

actually did check the alternator today..with truck idling, and both batteries connected, was getting 12.4v at the large terminal on the back of the alternator..if you read my earlier posts, I changed the alternator twice the other day...battery light stayed on with both...2- bad alternators, each from a different warehouse, possible? but a long shot in my mind...
Peter