4000 indicator lights

72supr

Member
I can't get my alt light to come on when I turn the key on my 1972 JD 4000. Put a test light on alt in wire that is not looped on alt then light will glow but will glow all the time.Put a new alternator on this spring I believe light was working with old alternator.New one is nippondenso.Air filter light won't work either when key is turned further just before start. Any help much appreciated.
 

If wires are good leading to air cleaner switch and ground wire is making good connection then I'll guess faulty air cleaner switch. Have you checked wiring connections just in frt of firewall?

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Test all the circuits, study the schematic in the tech manual. Get out your multimeter. If you put in a Nippo alternator the circuit could be different. I can't comment further about the Nippo without knowledge of that upgrade. That being said most circuits back then were pretty straightforward and can be traced to a ground or feed issue.
 
"Put a test light on alt in wire that is not looped on alt"

Can you explain what that means?

Next, DOES the alternator charge when the engine is running?

Was the old alternator a Nippondenso or a Delco?

IIRC, the "excite" terminal on a Nippondenso doesn't draw as much current as a Delco, and MAY not be able to light the same indicator lamp as a Delco can.

"Air filter light won't work either when key is turned further just before start."

That is a "lamp test" terminal/feature of the ignition switch, might be a bad switch or loose/dirty connector there, can't remember if there's diodes involved, as there are on other/newer stuff.
 

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