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Hey Moose...alternator wiring question

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EDNY:
Moose...did review your tech post...

I am wiring my Delco 3 wire alternator, already have the battery and sensing plug joined. My question relates to the exciter wire...read somewhere that it could simply be connected to the starter solenoid (purple wire).

What do you think...since  there wouldn't be any possibility of power back feed with key off? (and one less wire through the firewall). If you still recommend the ignition switch will a 3amp diode be OK? (Radio Shack IN5402)

Ed

themoose:
Ed

Hooking the exciter circuit to the S terminal will work in theory but I don't recommend it because any solenoid will generate a fairly high voltage spike in the circuit when B+ is removed and the field induced by the coil windings brakes down. That spike would most likley cause a failure of the diode triode for rectifier. I recommend using a diode and an inline 10 ohm [2 watt + ] resistor  installed in series in that wire, [that resistor isn't required for the alternator to actually operate, but is put there to protect the diode trio inside the alternator from damage due to a power surge. One other thing you might want to consider is the sensing wire. You often see the B+ and the sensing wire joined at the alternator but the best way to do it is to go to your power distribution ( fuse box) and tie in there. That way you are sensing demand of your electrical components so the alternator can better compensate for the various loads and not just sense battery state. I usually use an 1N5408

Moose

EDNY:
Thanks..

The only reason I mentioned the Radio Shack IN5402...is because a already have a few of them in my tool box.

The TPI setup already has a couple dozen wires going through the firewall. I used (2) Deutsch 12 pin weather pack plugs through the firewall to the ECM. If I need to pull the engine...no need to unplug any sensors on the engine...just the (2) Duetsch plugs and out comes the engine.

Thanks
Ed

themoose:

--- Quote ---The only reason I mentioned the Radio Shack IN5402...is because a already have a few of them in my tool box.
--- End quote ---

Ed
I always do overkill when it comes to electrical components. I attached the spec sheet for 5400 series diodes and as you can see the IN5402 should do the job. When I buy the stuff I usually get the highest rating that I can but in reality you probably don't need anywhere near the capacity that the 1N5408 will handle. I hate to see those diodes wasting away in your tool box :-\

Moose
 

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