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Old 12-26-2018, 09:38 PM   #3
dmjlambert
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Join Date: Apr 2016
Location: Cypress, TX
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Re: engine harness wiring/1wire alt

More info: the brown wire gets positive voltage when the key is on, but the voltage goes through a brown and white resistor wire and on some trucks also through an indicator light bulb that is between the ignition switch and the firewall connector. So it's not full power 12V as if straight from the battery positive terminal. There is normally some resistance involved.
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