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Old 01-26-2018, 11:26 AM   #1
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Join Date: Dec 2011
Location: Yuma Arizona
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Idiot ? Light that is...

Converting the alternator on my 85 to a CS type. Plug has 2 wires: brown (resistance- L terminal) and a pink/blk (ign?-F terminal).
May sound stupid but, I don't think I have an alt indicator lamp. With key on, there's nothing present BUT I do have a voltage guage which currently doesn't work. I guess my question is, did they only have one or the other, not both?
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Old 01-26-2018, 05:44 PM   #2
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Re: Idiot ? Light that is...

Yes, they had one or the other but not both.

Trucks with the basic warning light style cluster had a "GEN" or "BATT" light wired to the alternator.

Trucks with the factory gauge clusters had a special resistance wire (in the cab / dash harness) to take the place of the warning light. And used a voltmeter (or ammeter in earlier years) to monitor the charging system.

The built-in factory resistance wire is only about 10Ω and the CS series alternators require a minimum of 35Ω in the circuit connected to their "L" terminal. So you'll want to add some additional resistance. I believe there are some plug conversion adapters available with a built-in resistor specifically for this purpose.
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