Batterylight with no problems
Batterylight with no problems
Working on my brother's truck, it's a 98 F150 2wd with the 5.4 in it. Recently the alternator took a dump and had to be replaced on the truck. The job was done by the book, but when we got done doing it the battery light was still on. The truck was driving fine and no noticeable problems from the electrical system after the repair. It was taken to Auto Zone and both the new alternator and the battery were tested and they both tested good. Still on his gut feeling he took the new alternator back off and swapped out for another one under the warranty. Unfortunately it was a new alternator but with the same battery light problem. We've even taken the batteries from both our trucks and swapped them, running on my battery he still had the battery light. I alsodid a search and I read about someone who had a similar problem after replacing the alternator, they replaced the mega fuses and got their light to turn off, that didn't work on my brother's truck either. I'm left to the battery cables, but i've already taken my multimeter and I cant find any drop in voltage and no high resistance on them.
Any ideas on what's going on here? The battery cables are Ford specific and i'm thinking Ford will want a good chunk of change for a full set of them. I'm just stumped to hell over this problem.
Any ideas on what's going on here? The battery cables are Ford specific and i'm thinking Ford will want a good chunk of change for a full set of them. I'm just stumped to hell over this problem.
Senior Member
Joined: Jul 2004
Posts: 6,200
Likes: 39
From: Easton, Pa.
If you look at a Haynes repair book on page 12-17, you will see an inline 20 amp fuse.
Is it blown?
See if the alternator has a org/lt blu lead off the alternator and trace it to the fuse holder.
The charge lamp is in series with the ignition switch from 12 volts off the battery and to the alternator regulator. The regulator grounds the lamp circuit at the alternator, so it lights.
As soon as the alternator begins output, the regulator opens the lamp circuit putting the lamp off.
If the alternator is not able to do this, the light stays on proving the charge lamp circuit is good or is grounded in between..
Best to check the charging voltage. You might find the alternator is not charging due to a bad plug or an open small fuse.
Testing the part is fine but they must all work when hooked up.
Is it blown?
See if the alternator has a org/lt blu lead off the alternator and trace it to the fuse holder.
The charge lamp is in series with the ignition switch from 12 volts off the battery and to the alternator regulator. The regulator grounds the lamp circuit at the alternator, so it lights.
As soon as the alternator begins output, the regulator opens the lamp circuit putting the lamp off.
If the alternator is not able to do this, the light stays on proving the charge lamp circuit is good or is grounded in between..
Best to check the charging voltage. You might find the alternator is not charging due to a bad plug or an open small fuse.
Testing the part is fine but they must all work when hooked up.