Alternator light stays on

[JimR]

I have a 7275 Cub Cadet that has an alternator light that will not go out. I have 12.6 volts at the battery when the motor is off. With the motor running I have 14.70 volts. I also have the same at the back of the alternator when shut off and running. I've been using the tractor like this for months so I know that it is in fact charging. What is keeping my light to stay on? Could it be just a bad connection at the light bulb itself?

 

[CCWKen]

I believe this type alternator (Mitsubishi) uses a line from the ignition switch (on) to the light. Then from the other side of the light to the "L" contact on the alternator. Check this last wire from the light to alternator for a short to ground. Also, release/pull the connector from the alternator and slide it on and off a few times. There may be corrosion at the connector.

Have you done anything to the tractor lately? Like replace the ignition switch or light bulb?

 

[JimR]

I believe this type alternator (Mitsubishi) uses a line from the ignition switch (on) to the light. Then from the other side of the light to the "L" contact on the alternator. Check this last wire from the light to alternator for a short to ground. Also, release/pull the connector from the alternator and slide it on and off a few times. There may be corrosion at the connector.

Have you done anything to the tractor lately? Like replace the ignition switch or light bulb?

I have 12 volts at both wires on the connector that you mention. I do have the repair manual for this and that is part of the test. I didn't see where it had any checks for the light. I haven't done anything to the tractor in quite some time to cause this. I also checked the fuses for a bad connection.

 

[CCWKen]

With the key on (not running), you should have battery voltage at both wires at the connector. The one from the light will be a little less since Bv is going through the resistance of the lamp. Does the lamp illuminate with the connector off the alternator and key on?

 

[CCWKen]

Forgot to mention: Since you have the book, check to see if this light is also a service light or warning light for some other function. It may serve a dual purpose. If the light is on when the connector at the alternator is disconnected and the key is on (not running), the wire is grounded. BUT... this could be from another sensor.

 

[JimR]

Forgot to mention: Since you have the book, check to see if this light is also a service light or warning light for some other function. It may serve a dual purpose. If the light is on when the connector at the alternator is disconnected and the key is on (not running), the wire is grounded. BUT... this could be from another sensor.

I have 12 volts at both wires when that connector is unplugged. My light is still on when it is disconnected. A short sounds like it may be the problem. I did notice that over the last few months that the light is sometimes off. I also noticed tonight when I was messing with it that the insulation on the wires at the alternator are brittle. Maybe there is a problem with the wiring harness itself. Pulling the light fuse kills the charging idiot light.