Rich Ackermann 174 Report post Posted October 5, 2020 I have a 70 mach 1 351C with a factory tach. My understanding, which could be completely wrong, is when converting to a one wire Alternator, the stock Alternator/Regulator wire harness is eliminated and you run one wire from the alternator to the battery side of the Starter Sednoid or directly to the battery. If my understanding is correct, then how do I rewire the Black/Yellow Accessory and Red/green 12v constant wires (see picture below Circle "A". I believe both of these wires have constant 12v with the ignition switch is in the any position, including off. In other words, when converting to a one Alternator, where do I connect the two wires in circle "A", if the plug in circle "B" is gone? Do I just cut the plug ("A") off and add an inline fuse and connect them to the battery side of the Starter Sednoid? Thanks, Rich Quote Share this post Link to post Share on other sites
Midlife 814 Report post Posted October 5, 2020 First off, the yellow/black wire on the underdash harness side is incorrect; it must have been spliced into a green/red wire further up. You can simply ignore the two pin plug (A) if you run a thick wire directly from alternator to battery side of starter solenoid. Or simply plug your alternator harness into the large pin in plug A, leaving the other wires unused. Quote Share this post Link to post Share on other sites
Rich Ackermann 174 Report post Posted October 6, 2020 1 hour ago, Midlife said: First off, the yellow/black wire on the underdash harness side is incorrect; it must have been spliced into a green/red wire further up. You can simply ignore the two pin plug (A) if you run a thick wire directly from alternator to battery side of starter solenoid. Or simply plug your alternator harness into the large pin in plug A, leaving the other wires unused. Midlife, According to the wiring diagrams the green/red wire is 904 from the ignition switch to the alternator lamp pin on the circuit, board and then is 904A to plug "A" and then to the voltage regulator. My mistake the other wire it is 38 black from from the alternator to plug "A" where it is joined with 152 yellow to the regulator, and thru plug "A" as 38 black to the battery side of starter then as 38A it becomes 37 black/yellow stripe to a splice with 21 yellow to ignition, 25 black/orange to headlight switch, and 37A to a 20 amp fuse in the fuse box and on to 383 red/white for the emergency flashers I don't think i can leave these disconnected. Seems to me that 38 black should connect to the battery side of the starter only. Not certain what to do with 904-904A. But it seems to me that if I leave it disconnected my alt warning lamp will nolonger work. Quote Share this post Link to post Share on other sites
Kris 90 Report post Posted October 6, 2020 The two plugs you are talking about are for the alternator. To do a one wire alternator you simply do away with the original alternator wire, ignore the plug off the harness that it plugged into, and remove the voltage regulator. You want a one wire alternator with a built in regulator. I’m pretty sure the light on the dash won’t work after this so that would be a question for midlife if it’s even possible if your worried about it. Your amp gauge will also no longer work. Quote Share this post Link to post Share on other sites
Rich Ackermann 174 Report post Posted October 6, 2020 6 minutes ago, Kris said: The two plugs you are talking about are for the alternator. To do a one wire alternator you simply do away with the original alternator wire, ignore the plug off the harness that it plugged into, and remove the voltage regulator. You want a one wire alternator with a built in regulator. I’m pretty sure the light on the dash won’t work after this so that would be a question for midlife if it’s even possible if your worried about it. Your amp gauge will also no longer work. Thanks Kris. Its a factory tach car so I don't have an amp gauge. Only have an alternator light. Quote Share this post Link to post Share on other sites
Midlife 814 Report post Posted October 6, 2020 Then you'll have no means of monitoring your charging system, which is why I dislike the one wire alternators. The thick wire on Plug A is also tied directly to the power lead of the main harness at the battery side of the starter solenoid. The purpose of that Plug A is two fold: provide a path from the alternator to the+ side of the battery, and to provide a signal for the alternator indicator lamp (if tach configured) or to stimulate the voltage regulator (if standard dash). With a one wire alternator, you simply run a wire from the alternator output to the battery side of the starter solenoid, effectively bypassing Plug A. Or, you can plug that alternator wire into Plug A, which already has a path to that starter solenoid location. Quote Share this post Link to post Share on other sites
Rich Ackermann 174 Report post Posted October 6, 2020 37 minutes ago, Midlife said: Then you'll have no means of monitoring your charging system, which is why I dislike the one wire alternators. The thick wire on Plug A is also tied directly to the power lead of the main harness at the battery side of the starter solenoid. The purpose of that Plug A is two fold: provide a path from the alternator to the+ side of the battery, and to provide a signal for the alternator indicator lamp (if tach configured) or to stimulate the voltage regulator (if standard dash). With a one wire alternator, you simply run a wire from the alternator output to the battery side of the starter solenoid, effectively bypassing Plug A. Or, you can plug that alternator wire into Plug A, which already has a path to that starter solenoid location. Randy, as you pointed out plug A does have a path to the battery side of the starter solenoid by way of a splice before plug A that has a black pigtail wire and a post hole connector which I suspect connected to the battery side of the starter solenoid. This would also then supply constant 12v back to the the thick black wire 38 to the black / yellow stripe wire and on to the ignition and flashers and headlight switch, etc... according to the wire diagram. I attached the wire diagram to my previous post. Quote Share this post Link to post Share on other sites
Stevewr54 12 Report post Posted October 18, 2020 You might want to read the article on the www.madelectrical.com website. It gives some good information about 1-wire alternators. Steve Quote Share this post Link to post Share on other sites
Rich Ackermann 174 Report post Posted October 18, 2020 16 minutes ago, Stevewr54 said: You might want to read the article on the www.madelectrical.com website. It gives some good information about 1-wire alternators. Steve Thank Steve. I'll do that. Quote Share this post Link to post Share on other sites