Generator to Alternator

[blackbeard]

I am converting my 1959 12 volt Chevrolet truck with 235 from generator to alternator. I am using all the original gauges and want to make sure the ammeter will work. For those that have done this what is the best alternator to use a one wire or a three wire? How many amps would be sufficient? Will my original gauge work with a alternator? My truck will be pretty much stock with the exception of adding a radio. I may eventually add ac but I am not doing that at this time. I have purchased the alternator bracket from our host and am replacing all the wiring with their classic wire update harness from aaw. Thanks for all responses!!

 

[Bill Hanlon]

I replaced the generator (it quit on me) on my 57 GMC with a 1 wire alternator. Worked OK for many years. This truck had A/C and a radio. It came from the factory with an idiot light, so I replaced it with an ammeter from a 55 GMC.

When I bought my current ride, a 52 GMC, it had been converted to 12 volts using a 1 wire alternator and a set of aftermarket gauges that included a volt meter instead of an ammeter. I noticed that the voltmeter read lower than I thought it should. Even at cruising speed, the meter would only read about 13 volts, less with the lights on and A/C running. I verified with a digital voltmeter that the battery was only seeing about 12.8 volts with the A/C fan on high. Not enough.

1 wire alternators are easy to install, but have a basic flaw. The internal regulator can only measure voltage at the output of the alternator. It cannot sense voltage back in the system. I took my alternator apart and replaced the internal 1 wire regulator with a 3 wire regulator. I connected the sense wire for the alternator back to my fuse block "hot" side. Then the regulator could "see" what was going on under my dash and adjust the output of the alternator to provide proper voltage. Now my truck cruises at 13.8 volts, lights on, A/C on full and the tunes up loud.

Forum member Bilbo had a 3 wire alternator, but had connected the sense input directly to the output of the alternator, effectively converting his 3 wire alternator to a one wire. His truck, also A/C equipped, suffered from lower than desired voltage under heavy electrical load. We moved the sense wire source back under the dash and his system voltage jumped back to where it should be.

 

[coilover]

Used to convert to alternators on farm and construction equipment all the time. Would use an internal regulator alternator (didn't have one wire units back then) and simply run a wire from the battery terminal on the back of the alternator to the #2 terminal where the plug fits into the side. Usually would self energize, especially if you revved it to 1500 or so, and if it didn't a wire from the accessory terminal on the ignition switch to the #1 at the side plug would fix it up. Had people that used a wire from the + side of the coil to the #1 terminal and it charged fine---just couldn't turn the engine off. A wire from the alternator battery terminal to the wire that was on the "BAT" terminal on the old generator voltage regulator will have all the gauges work as before.