Alternator light staying on

[timmyb]

Hello, I have a 72 Ford pickup with 300 six and 3 on the tree that I am in the process of making road worthy. The truck had sat for several years but I was able to get it running. I replaced the alternator, voltage regulator, and battery. I believe the system is charging because I am getting 14 volts at the battery with the engine running and I can disconnect the battery terminals from the battery and the engine continues to run. However, the alternator light stays on. I double checked and cleaned all of the connections and mounting points on the regulator but this did not resolve the light staying on issue. Any ideas as to what could be causing this light to stay on and how to fix it?

[fordman]

could be a loose alternator belt. or faulty wiring to the light. checxk this diagram for a 69 with dummy lights instead of gauges to see if everything is wired right. http://www.fordification.com/tech/wirin ... rging2.jpg there is anohter diagram for the 72 but it doesnt show the dummy lights in that diagram.

[Thunderfoot]

This light is controlled by a circuit inside the Voltage Regulator, that part of it could be bad, a new Regulator would fix it if that is the problem. Only other thing would be if the wire from the light to the Voltage Regulator has shorted out somewhere it will make the light come on.

[70_F100]

This light is controlled by a circuit inside the Voltage Regulator, that part of it could be bad, a new Regulator would fix it if that is the problem. Only other thing would be if the wire from the light to the Voltage Regulator has shorted out somewhere it will make the light come on.

One other thing. If the light is dim, it's probably a bad diode in the alternator. If it's the right one (isolation diode), you will still get voltage that is really close to full voltage, but the light will come on dimly.

Remember that even new (or rebuilt) parts can be defective.

[towtruckerfour]

Every once in a while on my 70 F250, the light might stay on. All I do is turn the key back just a hair towards off and it goes out. Truck has no issues so not sure what causes it.

[fordman]

bad ignition switch causes that. it wont spring back on its own. my 88 in the column switch does that. i have to turn it back just a slight to get the warning light to go off.

[Thunderfoot]