Jim Grant's Tech Tips
Ford LTD, Charging System
Q: I own an '85 ford LTD
with a 3.8 liter engine. The charging system is not charging the battery.
I have changed the alternator and voltage regulator. Still, I have no
charging light and the system is not charging. What is the problem?
sounds as if your alternator is not being told to charge. The reason for
your problem could very well be related to the Charge Light on your dash.
The charging system on your vehicle needs to know when the ignition switch
is on. When the ignition switch is on, electricity from the switch travels
through a wire to the Charge Light on your dash. From the Charge Light,
the wire continues out to the voltage regulator, which completes the circuit,
to light the bulb. This electrical signal also cues the voltage regulator
to activate the alternator, once the alternator's charging the light goes
out. It's a reasonably simple electrical circuit.
non-functioning Charge Light indicates the following possibilities; a
defective voltage regulator, a bad electrical connection or broken wire
to the voltage regulator, a failed Charge Light bulb and resistor (the
resistor is a backup in the electrical circuit in case the bulb fails)
or there is no electrical power from the ignition switch.
your technician determine if the electrical signal to activate the charging
system is present at the voltage regulator with the key on. If the activation
signal is present then there's a problem with the voltage regulator. If
not, then you'll have to check the wiring.