Gen 2 Exciter Circuit

[bchesley]

I have been rewiring my alternators from a previous owners debacle and now have the wiring corrected per the TM's. I was missing an isolated ground alternator so I got one from Old Mechanic and it test good. Now both alternators that tested good are installed in the truck. I turn the key on and get only a Gen 1 light. I have already replaced the relay for Gen 2 and the Voltmeter with CUCV Electric relays. I have replaced both bulbs for the Gen lights. I have also checked for power to the relays and they both kick on with the key in the run position.

My searches on the subject revealed that the order of power should be Gen 2 light bulb to the Gen 2 Relay to the Gen 2 Diode, to the Gen 2 plug. Is this correct? I am getting nothing on the brown wire at Gen 2 and want to make sure I go in the right order. Can a bad light socket really kill the alternator exciter circuit? Thanks.

Brad

 

[ryan77]

Yes if the circuit board wiring is bad on the cluster your exciter wont work, ive had to run a jump wire from the plug wire to the actual bulb due to the circuit board on the cluster being bad. Check and see if you have power to the wires on the back of the plug going to the cluster if you do then the printed circuit board on the cluster has a break or short.

 

[bchesley]

I think that I have good news, but still a question. I traced voltage all the way to and from the relay under the dash. From there I could not get to the Diode because I have not taken apart the dash. I am still stumped how or why it will not light up. If there is voltage to the relay should it not light up and then when the alternator charges is goes out? Or will completing the circuit to the alternator make it light up and then go out when it starts charging? This system is dang confusing....

 

[ryan77]

Theres power from that gen 2 bulb that comes on when the key is on to the alternator excitor wire i dont remember the color wire but u want to trace it from the bulb cluster all the way to the alternator its probly the bulb or the printed circuit if u have no power to the plug!! Try multiple bulbs i had one truck where i had 3 new bulbs that were defective!

 

[bchesley]

That is confusing to me, because if I have power to the relay it already got past the Gen 2 light socket correct?

 

[ryan77]

Check for power at bulb before u do anything else! I dont have wire diagrams in front of me im out of town and using my phone to post! Check the gen 2 bulb for power maybe sent warthog a pm about the diagram!

 

[mistaken1]

Does this help? Courtesy of UncleSam (member who colored the diagram)

The way I read the diagram if you have power at the relay but not at the alternator the problem lies between those to points. Could be the diode, or wire or a bad connection/terminal along the way.