Electrical Issues
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Electrical Issues
I have an 87 F-150 4.9L and I am having some issues with the battery charging. I have had the alternator replaced and the battery has been tested so both are good, but my voltage gauge reads nothing (it might just not work) and my battery light is now on. When I drive at night with the headlights on it drains the battery after a while so it is not be charging while the truck is running. I have heard people talk about a voltage regulator but I am not sure if I have one or where it might be. I'm also not sure if that's the problem. I would appreciate any help anyone can provide
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Joined: Dec 2007
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From: Boise, Idaho
I don't remember if they went to alternators that have built in voltage regulators, but if not, then that's probably it. I had this same issue on my '81 and that fixed it. The voltage regulator is an (approx.) 3in x 3in box on the fender next to the battery. They're about $20 new.
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just thinking out loud-
maybe the trigger wire on the regulator (the one that tells the alternator to start charging) isn't connected? unsure on the '87, but i think these wires were usually green. should be the "I" wire.
maybe the trigger wire on the regulator (the one that tells the alternator to start charging) isn't connected? unsure on the '87, but i think these wires were usually green. should be the "I" wire.
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From: In my own world
that's a 2 g set up, known for melting the harness that plugs into the alternator.
To test the key wire, it is the green/ red tracer wire. My bet is diode in the alternator went bad from bad connection. You can replace the connection with a harness patch, or go ahead and up grade to the newer 3 g set up. I have been doing that with all my g2 trucks as they start to give me problems.
I have a g3 install thread if anyone is interested in the upgrade, I will look it up, and post a link
To test the key wire, it is the green/ red tracer wire. My bet is diode in the alternator went bad from bad connection. You can replace the connection with a harness patch, or go ahead and up grade to the newer 3 g set up. I have been doing that with all my g2 trucks as they start to give me problems.
I have a g3 install thread if anyone is interested in the upgrade, I will look it up, and post a link
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FTE Legend
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From: In my own world
Fuseable link, black/ orange tracer, comes off the solenoid
I'll find it and link it when I get home later
I'll find it and link it when I get home later
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From: In my own world
Ok, here is the thread I spoke of. there are others, but this one will give you the basics. The whole thread is a good read, but I started the swap instructions on page 3, or post # 32, depending how you have your browser set up.
https://www.ford-trucks.com/forums/1...ator-help.html
Let me know if you need any other info
https://www.ford-trucks.com/forums/1...ator-help.html
Let me know if you need any other info
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