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3gswap.jpg | Hits: 16001 | Posted on: 5/26/11 | View original size (347.12 KB)

1G-to-3G (or 4G) Swap Wiring
IF THE IMAGE IS TOO SMALL, click it.

Compare to: . . . . . . . . . . . . . . . See also:
. . . . . . . . . . . . . . .

Note that the 3 wires going to the new voltage regulator connector are stock early Bronco voltage regulator circuits used for their original functions, so this swap is easier than it appears. Just splice them onto the 3G VR pigtail (WPT-119). Circuit 26 should NOT be connected to 37; cap each one off separately. Or, 37 can be attached to C211 to increase the current-handling capacity at S204.

The only real electrical modification is the addition of an inexpensive 4ga battery cable (eye-to-eye) available at any parts store for $5-10, and a 175A fuse w/holder (or similar circuit breaker) which is slightly harder to find, but still not expensive. But it might be cheaper & easier (by eliminating the 152-Y splice at S-201) to just grab the whole setup from a later junkyard vehicle, like this:



Since the stock '66-77 charge wire (37 Bk/Y) is too small to carry the new alternator's output, the stock '66-77 ammeter is equally useless after this mod (not that it was much good before), so a voltmeter is a logical replacement for it, and there are writeups for swapping one into the stock cluster on ClassicBroncos.com, and in this album:



This shows the MILDEST consequence of an alternator upgrade keeping the stock ammeter:



It COULD have been much worse - a fire in the dash with a dead short to the battery through a relatively heavy wire.

Although the 904 Gn/R connection to S203 is required, the ALT bulb & resistor aren't necessary for the alternator to work properly, but it's an inexpensive, easy, & effective addition to the circuit. The bulb only lights if the VR detects a fault (or before the engine starts). The resistor maintains the circuit if the bulb burns out, but doesn't interfere with the working bulb. A bulb holder with the correct resistor can be found in many Fords from the mid-80s to early-90s.



The choke heater shown is a stock 6V heater. For an aftermarket carburetor with a 12V heater (check it documentation), the best place to splice it is on circuit 932 Bu, which already goes to the carburetor area.

An aftermarket voltage regulator is available (commonly referred to as "1-wire", even though it needs 2 in addition to the charge cable) which eliminates the need for the LG/R wire and the option of the ALT lamp. Some exhibit intermittent charging problems and battery drains, but many work fine.

Thanks to Viperwolf1 for valuable input.

If the 3G doesn't quite fit the engine bracket, read this caption & the NEXT few:



Don't overlook the battery terminals or alternator mounting. Not only will poor connections prevent a high-output alternator from putting out its max; they can cause a WIDE variety of other symptoms & problems.

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