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A. Penland
A. Penland, Ford Senior Master Technician, ASE
Category: Ford
Satisfied Customers: 6169
Experience:  ASE Master Certified, ASE Advanced Gasoline Engine Performance
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1986 ford f-150: 300 6cyl, machanical fuel pump..charging system

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I have a 1986 ford f-150, 300 6cyl, machanical fuel pump. The problem that I am having, is the charging system. I have replaced the battery and the altanater. Someone said it could be the brain box. I have tried 3 altanaters and 2 batteries, they were all new.


What is the main problem you are having with the charging system?
Where are you measuring the voltage for the system?
On the dash guage or with a meter?

Customer: replied 6 years ago.
I am testing from the battery, but factory gauge is reading about the same.
What problems are you having?
Dim headlights, erratic guage, having to jump start it in the morning?
Customer: replied 6 years ago.
not charging ! some times it does charge. replaced wires to altanater, replaced gauge cluster, thought it might be that cheap ribbon behind the gauges. when it is charging you turn on the lights, the voltage drops down on the meter that is conncted to the battery. I have checked continuity through all of the fuseable links,
Ok. Well your vehicles computer (Brain Box) is not part of the charging system. You either have a bad positive cable, negative cable, or ground that is not always making good contact. Check the engine grounds and check the resistance in the battery cables to the engine, alternator, starter, and all the grounds. You may also have a poor ground to the headlights. High resistance in a circuit requires more current to get through the resistance. Basic Ohms Law.
Customer: replied 6 years ago.
I have a ground wire from the battery to the altanater. gound cable has been replaced and the hot cable to the starting celanoid has been replaced, the only cable that hasnt been replaced is the one from the celanoid to the starter, it starts just fine, when it is charged.. I even went to a extreem, I disconnected the headlight plug end from the headlight and made wires from the battery to the head light, and still had the same effect,
Check the voltage at the alternator when the engine is running and the lights are on. See if you get a higher reading at the alternator then at the battery.
Customer: replied 6 years ago.
what is it if I higher reading at the alternator than the battery ?
Then either the battery negative cable is bad or the wire from the alternator to the battery has high resistance. You can also have a poor connection in the cable from the alternator to the battery.
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Customer: replied 6 years ago.
forgot to tell you , I can take the battery out of the truck while it it still running, And it still runs, and tests 14.5 volts on the battery cables. I put the battery cables back on the battery, and it and still have the same problem, I have tried 2 new batteries.
It sounds like a poor contact or connection either to ground or a connection have resistance in it. With the battery out, the alternator is full fielding and charging at it's max, 14.5 volts. You put the battery back in, and the battery becomes a load, and the charging system voltage drops. I am still leaning towards cleaning all connections and making sure you have a good connection at the starter solenoid(relay).
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Customer: replied 6 years ago.
I asked you a question on jan 31, and over paid you . I contacted pay-pal and they sent you an E-mail about this, and I have not received any money back to my account, I wanted to pay you $23.00 not $52.50. I need the $29.50 credited back to my pay-pal account. any questions call Jerry at XXX-XXX-XXXX

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