A thread for my ignorant wiring questions...

PostPost by: steve lyle » Tue Aug 13, 2019 2:00 am

I'm in the middle of rewiring the dash on my Federal Sprint to fix a myriad of issues So far, so good on what I've tested, outside of one circuit. I'll ask for help from the hive on that one, but use this thread for any others that might come up.

So, the issue now is the alternator light. Turn the ignition to "on", and it should light. It was originally on the white circuit, I'm putting it on the green (white/fused) circuit, fwiw. It's grounded by the brown/gold wire coming out of the back of the alternator, which is at ground with no alternator output, and sees the alternator output. So when alternator output is approx battery voltage, the light goes out.

So that's my understanding of how it should work. It worked before I tore into the wiring. Now it doesn't. And the reason is that the terminal in the alternator that the brown/gold wire connects to has 5k ohms between it and ground. If I disconnect the brown/gold at the alternator, and ground it, with the key on, my light comes on. Remove the ground and insert it back into the alternator, and no light. The alternator case itself is perfectly grounded - 0 ohms between it and the ground wire at the dash (when I ground the brown/gold on the case, the light works).

The alternator is the DBE conversion, with the original 2-wire plug on the back with brown/gold and white wires. Nothing has changed about it during this rewire operation.

I must be missing something pretty simple, but I'm stumped. Any ideas?
Steve Lyle
1972 Elan Sprint 0248k @ https://www.mgexp.com/registry/1972-Lot ... 48K.30245/
1972 MGB Roadster @ https://www.mgexp.com/registry/1972-MG- ... 842G.4498/
2007 BMW 335i Coupe
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PostPost by: steve lyle » Tue Aug 13, 2019 2:27 am

Mystery solved. The "excite" wire - the white one that's in the same connector at the back of the alternator with the brown/gold, was not hooked up.

Stay tuned for my next "doh".
Steve Lyle
1972 Elan Sprint 0248k @ https://www.mgexp.com/registry/1972-Lot ... 48K.30245/
1972 MGB Roadster @ https://www.mgexp.com/registry/1972-MG- ... 842G.4498/
2007 BMW 335i Coupe
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PostPost by: geni » Tue Aug 13, 2019 5:49 am

Je doit re-cabler le tableau de bord sur S4 SPRINT LHD mais ne sachant connaitre la position du passage du faisceau electrique , l'ancien ?tant enlev? ! (je n'ai pas de soucis de connection aux instruments) mais uniquement de la position exact du harnais pour sont placement exact
Donc si vous pouvez en faire des photos cela pourrais bien aider

I must re-cabler the dashboard on S4 SPRINT LHD but not knowing the position of the passage of the electric beam, the old being removed! (I do not have trouble connecting the instruments) but only the exact position of the harness for exact placement
So if you can make pictures that could help
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PostPost by: steve lyle » Tue Aug 13, 2019 7:19 pm

geni wrote:I must re-cabler the dashboard on S4 SPRINT LHD but not knowing the position of the passage of the electric beam, the old being removed! (I do not have trouble connecting the instruments) but only the exact position of the harness for exact placement
So if you can make pictures that could help


Sorry, I didn't take any pictures that would help you. Mostly because they wouldn't help me, because I didn't trust that anything was original about my current wiring. Too many things weren't working, too many splices, too many wires routed where you knew they shouldn't be. So I'm working it out as I go.
Steve Lyle
1972 Elan Sprint 0248k @ https://www.mgexp.com/registry/1972-Lot ... 48K.30245/
1972 MGB Roadster @ https://www.mgexp.com/registry/1972-MG- ... 842G.4498/
2007 BMW 335i Coupe
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steve lyle
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