1986 Ford F-150 charging problem

Tiny
JD_PEEKS
  • MEMBER
  • 1986 FORD F-150
Electrical problem
1986 Ford F-150 V8 Two Wheel Drive Automatic 126? Miles

truck not charging alt is good all grounds seem fine but only get 12 volts when running harness to alt is fine but when I unhook alt harness from round plug with 4 terminals that is just under solinoid the short that my test light says I have when hooked between pos term and ground goes a way also shorted from yellow wire that goes fron solinoid to engine computer when computer is unhooked that short goes away opened up computer but nothing in there looks shorted I dont know where to go from there also pulled fuses to locate short that did nothing
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Monday, October 11th, 2010 AT 12:37 PM

7 Replies

Tiny
WRENCHTECH
  • EXPERT
What is this short your talking about? How did you test or conclude this.
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Monday, October 11th, 2010 AT 12:51 PM
Tiny
JD_PEEKS
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Not sure what type of short I tested it with a test light between the ground wire and neg teerminal between batt.
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Monday, October 11th, 2010 AT 3:53 PM
Tiny
WRENCHTECH
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That's not a short. That is a parasitic draw and yes the alternator can do that.
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Monday, October 11th, 2010 AT 5:16 PM
Tiny
JD_PEEKS
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I thought sbout that but now the alt isn't even hooked up so now I dont know where to go from there any ideas before I go chasing all those wires around thank you for your time
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Monday, October 11th, 2010 AT 10:48 PM
Tiny
WRENCHTECH
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There is a procedure for finding a battery draw like that.

You will need a digital ammeter and a jumper wire with clips on the ends to do this.
First rig any door switches so you can have a door open without triggering the interior lights and unplug the hood light. Remove one battery cable and attach the meter in series between the battery cable and battery post. Take the jumper wire and also attach it the same way. Leave the jumper wire on for at least 10 minutes to expire all the automatic timers. Now remove the jumper wire and read the meter. Anything over 50ma is too much draw. The way you locate this is to start removing fuses one at a time until the meter drops to normal level. This will be the circuit with something staying on. Determine what components are part of that circuit and check them individually until the problem is isolated.
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Tuesday, October 12th, 2010 AT 4:28 AM
Tiny
JD_PEEKS
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Where do I hook up this jumper wire and also the fuse thing I was under the impression that if I pulled the fuses that the test light would go out on the faulty circuit this was not the case. I also hooked my digital multimeter betweem neg post and ground wire with it set to volts it reads just over 12 volts and this also doesn't change as I pull fuses so thinking problem lies before fuse box also do you have any way what the yellow wire from solinoid to computer does with this wire unhooked mt truck cranks and all lights work but it wont start with it unhooked. There is also a wire from solonid into alt, harness that when hooked up sets my test light off. That wire when disconnected shuts off all power to truck any chance that the two could be on same circut and if so which circut could that be. I cant read wieing diagrams very well and cant figure out which wire does what thank you.
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Wednesday, October 13th, 2010 AT 8:41 PM
Tiny
WRENCHTECH
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Just follow the instructions the way I gave them to you. You have to use a multimeter because the test light is only on and off and doesn't measure how much draw. You can't use the volt scale. You have to use amps for this to work right.

The jumper wire is parallel to the meter just until the timers expire so you get an accurate reading.
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Wednesday, October 13th, 2010 AT 8:50 PM

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