Battery Light
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New User
Joined: Jun 2010
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Battery Light
I searched, but couldn't find anything that has led me to a solution. Truck is a '99 F250, 7.3, crew cab, etc. My battery light has been on for a few days, and I can't figure out why. Alternator and batteries are less than a year old. I'm getting 14.2 volts at idle on both batts, and 13.3 volts with the engine off. Had the charging system load tested and everything checks out fine. Truck shows no symptoms of anything wrong, except the light. Obviously some parameter the ecu monitors is out of spec, but not sure how to find it. Any suggestions?
Senior User
Joined: Sep 2003
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From: SE Pennsylvania
In 1999 the ECu does not monitor the alternator. The battery light is turned on and off thru the voltage regulator in the alternator. It may all test good but the regulator is causing the light to shine in my opinion. If you have a black regulator, it will run without sense the light will be on, but it will charge fine. If you have a gray regulator it just leaves the light on and may or may not charge.
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Joined: Jun 2010
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Update with new lights
Sorry to dig up my own old thread, but I still need help. I swapped another new alternator in, and the light stayed on, and is still on months later, with no other apparent ill effects. Any more ideas?
On another note, my ABS light and parking brake light are staying illuminated now. The crazy thing is I don't even have ABS. I did ball joints and such a while back and there was definitely no sensor in or electrical connection to the hubs.
So I have multiple lights illuminated for no apparent reason...could this be a bad ground to the idiot lights or something like that?
On another note, my ABS light and parking brake light are staying illuminated now. The crazy thing is I don't even have ABS. I did ball joints and such a while back and there was definitely no sensor in or electrical connection to the hubs.
So I have multiple lights illuminated for no apparent reason...could this be a bad ground to the idiot lights or something like that?
Post Fiend
Joined: Jul 2005
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1. Reset all computers.
2. Charge batteries / load test both separately.
3. verify alternator output
4. If you still have the alternator light on --- suspect is pigtail, replace it.
Details on link below.
Give specific details as to the alternator you put in.
Post voltages test (after testing as per link) data.
Are you putting in a crappy rebuilt alternator?
If you are, put in one with 30 to 50% more capacity than the factory one if you have not added to the electrical load.
If you have... you need a even bigger one.
2. Charge batteries / load test both separately.
3. verify alternator output
4. If you still have the alternator light on --- suspect is pigtail, replace it.
Details on link below.
Give specific details as to the alternator you put in.
Post voltages test (after testing as per link) data.
Are you putting in a crappy rebuilt alternator?
If you are, put in one with 30 to 50% more capacity than the factory one if you have not added to the electrical load.
If you have... you need a even bigger one.
