CASE 2290 ALTERNATOR LIGHT

1175scott

Member
I recently put all new wiring harnesses less the dash harness on my tractor. Before i did this my alternator light on the dash worked. Now everything works correctly on the tractor except the dash alternator light. I have checked all the wiring and went through the troubleshooting guide in the service manual and everything checks out. Have power on both sides of the circuit board where the lamp socket twists in. I have tried a new alternator, circuit board, sockets and bulbs. The fuses are all good and all the wiring checks out. Power on both sides of the bulkhead connector. Can somebody tell me what the He** is going on? It is a later serial number tractor if that matters.
 
start at the alternator,is it working 14 volts?the big wire should be hot and at the 2 prong plug the one farthest from the big wire should be hot,the other one creates a ground,remember the ground completes the circuit causing the light.
 
Scott, does the light come on if you ground the wire at the alternator that goes back the harness? The alternator does not have a switch to turn the light off as it charges, rather there is 12V on one side of the bulb and the current travels back the wire to the alternator and is effectively grounded as the alternator is making no voltage so is at 0V---when the alternator starts to charge the voltage rises at the alternator and as the voltages balance at the dash light no currrent flow is going on so the light goes out, 12V each side of the bulb. you should not have 12V on each side of the lamp socket if the wiring is correct, grounding the wire at the alternator should turn the dash light on if the circuit is correct.
 
I have grounded both the plug(brown wire) to chassis ground and grounded the actual alternator to chassis ground. The circuit board is only hot on the one side until you install the socket. In my thinking if power goes through the socket the bulb should light up. When I grounded the alternator the light would still not come on.
 
(reply to post at 10:06:17 01/22/18)

When u turn the switch on the button in the bottom of the socket goes hot, you can check that with a test light, when you insert the bulb if the other side gets hot also you have a bad connection from the socket shell to the wire from the alternator connection.

If you have voltage on both socket wires it indicates an open circuit on the ground (alt) side circuit, the reason the test light will light but not the charge bulb is because the test light bulb takes so much less current that it lights and will not carry enough amps to light the main bulb. Post any other info you feel relevant to the discussion.
 

Forgot to mention, you should not have voltage on both points on the circuit board, not for sure which but one side goes to switch and the other to alternator, you could look at the copper circuits and see which one goes to multiple lights on the board and correctly assume that is the feed wire for the lights and the other would be the ground wire to the alternator, it will in all likleyhood be the brown wire in the dash plug also. make sure all the tabs in the dash panel connections are straight, they can get messed up and create some interesting situations.
 

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