Ignition light stays on

[Dono]

Hi All,
If I recall there was a thread on this several months ago. It grew in length and comments. Did the author resolve the situation? It'd be great if they could refresh me on the solution.
I finished reassembling and running my 71 Spitfire. All is good but the ignition light stays on.
Thanks, Dono

 

[MGTF1250Dave]

Aloha,

I copied this awhile back, although it applies to my TR3A with a generator the concept should be the same.

HOW THE IGNITION WARNING LIGHT WORKS:

Sounds like what you're finding on the yellow wire is correct (i.e. nothing when ignition is switched on, hot when engine running).

The white wire should be hot when the ignition is switched on AND when engine running. I would suspect the white wire is loose or poorly connected at either the bulb fitting or the ignition switch.

In case you don't know... with the engine running both wires to the bulb (yellow & white) are hot with approximately the same voltage -- under this condition the bulb is out. It is when one or the other has a lower voltage (or no voltage) that the bulb glows.

I suspect your car has an alternator so my guess is my yellow wire would correspond to a brown with yellow tracer coming from the alternator and a white wire coming from your ignition switch. I don't have a wiring diagram for your car so this is conjecture. I'm sure some will come along soon with a definitive answer.

 

[TR3driver]

Dave's explanation is basically correct. Could be a wiring problem (eg, brown/yellow on the wrong terminal), but more likely IMO an alternator problem (bad regulator). It's not unusual for the alternator to work otherwise, but of course the glowing light will eventually run the battery down.

 

[71MKIV]

Yea that's what mine did too. assuming that the light comes on with the ign switch.

put a new regulator in the alternator for 10 bucks. all mo betta now.

 

[Dono]

Steve, Randall, Dave,
Thank you for the great insight, will check into it this weekend. It has a new alternator, so the regulator portion s/b okay. Will advise what I find. Thanks! Dono