Hello

Im in the process of redoing my battery connections..Meaning the positive wire with the pigtail... the alternator wire and the 12ga feed into the car.. I have an internal alt regulator so that wire is N/A.

Is it possible that all these smaller red wires are 12 gauge? Especially the alternator positive and the pigtail.. It doesnt seem right.. I would imagine at least 8 gauge from the altetnator to horn relay.. Has anyone changed the gauges of wire from stock to thicker?

Thanks!

 

I'm guessing you don't own the 1970 Oldsmobile Chassis Service Manual (CSM) which contains the official color wiring diagram? The red wires are correctly sized at 12 gauge. Changing those wires to a thicker gauge will yield the benefit of being less resistant, but the 12 gauge is adequate & appropriate for the stock OEM configuration.

 

Yes, 12 gauge would seem a bit small, but you have what's known as a 3-wire alternator. With the 3-wire design, the factory designers figured out a way to make 12 gauge work as well as 8 gauge.

The red wire on your alternator plug-in fitting comes from the horn relay. It delivers the actual voltage at the horn relay to the alternator's voltage regulator. The regulator dials up the voltage of the alternator until the voltage measured at the horn relay is at the set point (~14 V).

If the voltage drop in the 12 ga output wire between the alternator and the horn relay were, say, 2 volts, then your voltage regulator would make the alternator output 16 volts. That way the voltage at the horn relay would come out at 14 V.

If you put in an 8 ga wire, the regulator would still keep the voltage at the horn relay at 14 V--so you would not have gained anything for the trouble and expense.

A 1-wire alternator does not have this feedback loop, so it would be important to make the output wire a very heavy gauge to minimize loss of voltage at the horn relay.

Look on page 12-26 in your CSM to see the wiring diagram for your internally-regulated alternator.

 

Gary - Well written.