1991 Ford F-150 Battery

  • 1991 FORD F-150
Engine Mechanical problem
1991 Ford F150 6 cyl Two Wheel Drive Manual

I have replaced the alternator, and cylanoid, and wires on my truck. It just keeps acting like the alternator is not charging. After setting a while it starts. However, it won't stay charged. You can't turn anything on in vehicle the battery just drains and it dies. Have to work tomorrow no way with out truck. I have worked on it all week end. Plz help
Thank you
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Sunday, March 1st, 2009 AT 4:57 PM

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NOTE:Ensure battery is fully charged and connections are clean and tight. Check alternator drive belt adjustment and alignment.

Ensure all accessories are turned off. Connect voltmeter to battery. Attach tachometer and start engine. Operate at 1500 RPM with no electrical load. Voltmeter reading should increase, but should be no more than 2.5 volts greater than battery voltage. Reading should be taken when voltmeter stabilizes.
With engine operating, turn heater or A/C blower motor to HIGH position. Turn on headlights to high beam. Increase engine speed to 2000 RPM. Voltmeter should indicate at least .5 volt more than battery voltage.
If voltmeter reads 2.5 volts or more greater than battery voltage, stop engine, and connect jumper wire between regulator base and alternator frame. Repeat CHARGING SYSTEM TEST.
If voltage is less than 2.5 volts greater than battery voltage, check ground connections on alternator and regulator. Repeat test once repair is made.
If overvoltage condition still exists, disconnect regulator wiring plug and repeat CHARGING SYSTEM ON-VEHICLE TESTING. If condition is corrected, replace regulator and repeat test.
If overvoltage still exists with regulator disconnected, repair wiring harness between alternator and regulator circuits "A" and "F". Connect regulator, and repeat tests once repair is made.
Current Drain Check
Ensure all accessories are turned off. Disconnect either battery cable. Connect a test light between battery cable and battery post. If light remains off, no current drain exists. If light comes on, check individual circuits to find source of current drain.
"S" Circuit With Ammeter
Disconnect regulator wiring plug. Connect positive voltmeter lead to regulator wiring plug terminal "S". Connect negative lead to secure ground. Voltmeter should read zero.
Turn ignition switch to ON position. Voltmeter should indicate battery voltage. If no voltage exists, check "S" wire from ignition switch for open circuit. Repair wiring and retest system.
"S" & "I" Circuit
Disconnect regulator wiring plug. Install jumper wire between terminals "A" and "F". Start engine and allow to idle. Connect voltmeter negative lead to ground. Connect voltmeter positive lead first to terminal "S" and then to terminal "I" of regulator wiring plug. See Fig. 8 .
"S" circuit voltage reading should be 1/2 of "I" circuit voltage reading. Replace regulator if voltage readings are correct. Remove jumper wire from regulator wiring plug. Connect plug to regulator, and repeat CHARGING SYSTEM ON-VEHICLE TESTING.
If no voltage exists, check for damaged wiring. Connect voltmeter positive lead to positive battery post. Remove jumper wire from regulator wire connector. Attach connector to regulator, and repeat CHARGING SYSTEM ON-VEHICLE TESTING.
Fig. 8: Identifying Regulator Connector Terminals & Installing Jumper Wire


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Sunday, March 1st, 2009 AT 6:00 PM

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