Modernized Engine Wiring

[OneOfMany]

Thanks for the explanation and the link wjajr. I never made the connection between the variations between AC/DC.

Grant

 

[BillGrissom]

Bill,
A second diode parallel in the reverse direction would also clamp voltage drop in reverse direction. However significant discharges without running alternator are often avoided to save the battery. It would be an extra expense without benefit.

You need the 2nd parallel diode to protect the ammeter for current flows the other way, i.e. when current is drawn out of the battery. In the factory wiring, all battery current goes thru the ammeter, except for a few under-hood loads, like starter current and horn.

I gave a link to the diode I used. Probably not the optimal choice, but cheap on ebay and looked like the "nestle head to foot & solder" would work, which it did. I'll re-post later if it fails. I won't be driving the car until I paint and redo the interior (after home repairs, etc).
Disclaimer - copy me at your own risk. Man up and don't whine if you try and break something.

 

[BillGrissom]

Please correct me if I am wrong:
Watts = Volts x Amps

And I'll agree when you are right. Correct, Power = current x voltage (DC or instantaneous if AC).

A 12g wire supports 2400 watts. Therefore a 12g wire in a car can support 200amps.

Incorrect. Current is the only rating that matters for a wire. The power dissipated in the wire is (current)^2 * (resistance). This power must be dissipated as heat and conducted away. The later is different between home installation and appliances, so different current ratings. The voltage rating of the wire is for when the electrical insulation breaks down (arcs to ground).

At the risk of confusing people, you also see the power loss written as (V^2)/R, but V here is not the 120 V or 12 V max in the circuit, but the dV (voltage drop) across the wire itself. Of course, if you connect the wire directly from your battery to ground, dV = 12V, but don't do that. Walter White did that on Breaking Bad to a jerk in a BMW.

 

[KitCarlson]

Silly me. I read your post and found the part number. You have made an excellent choice. It is a Schottky with excellent specs.

I am impressed, you do quite well electrically and mechanically.