hey del

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aaadave

aaadave

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del,i know this isn't a mopar question, but i know you can probably help with this. i'm changing a 55 chevy with gen. over to an alternator. i know you run the batt. terminal to the battery, but is there any way to use the original idiot light with the alt? if you can give me a hand with where to hook up the two wires on the alt. plug, i would highly appreciate the help. thanks, dave.
 
It depends on what alternator you are using. I'm not familiar with the GM stuff "later" but the old 10/12SI either internal or external regulator, is all set up for that.

Post a photo and part no.?
 
speaking of the 10 si, thats what it is. got one for a 75 chevy with internal reg. car is all original mostly. i'm installing a classic air system in it, and the compressor bracket takes an alt. i've read where they tie the red sensor wire in with the batt. hot lug, but not sure of the white wire. i'm with you, don't know much about chevys, just trying to get this thing buttoned up for my neighbor . dave.
 
OK, this is easy. No2 goes direct to battery, this is "voltage sense." Some guys just jumper it over to the alt output terminal. So long as you have a nice big charging wire, that's OK

No1 is the "excite" wire and it simply hooks to your existing old lamp connection. If you haven't found this, it is a small wire connecting to one of the old regulator terminals. You can confirm it by turning the key to run, and hooking it to ground through something like a tail lamp. (This is in case you have the wrong wire.) This should cause the "charge" light to glow.

Like so:

chargcircuit2.gif



Also...........do NOT be tempted to hook the no1 wire direct to switched ignition. Eventually, this will eventually fail the diode trio. If this is not a "one wire" and you for some reason don't want to use the old lamp, you can put a diode in series with the no1 wire

v6432.jpg
 
The GM alternators are the "Motorola design", and is in my 80's M-B cars. The most confusing part is the "excite" wire (post 4). I call it the "boot it up" wire. It initially needs a small current thru that wire, usually from a dash lamp, to get the internal Vreg to self-power. My M-B manual says if the BATT bulb doesn't initally light, to drive immediately to the dealer, presumably for an emergency bulb replacement (I bet dealers loved that). Actually, 3 bulbs on my dash provide boot-up current. At higher rpm, residual magnetism in old alternators can generate enough to boot it up (even w/ bulbs blown). After I changed to dash LED's, it doesn't boot at idle, but rev'ing slightly works. The bulbs go out once the alternator Vreg generates power, which also serves also as a "bulb test" function.
 
well, got the alternator wired up today. working like a champ. 13.7 volts at idle, and the charge light is working. thanks again del for the diagram. dave.
 
i'll see if i can dig out my old digital tomorrow and snap a few before she comes after it.
 
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