3 wire alternator hook up?

Keith Molden

Well-known Member
I know I've wired them several times years ago, but my mind just won't let me remember how to do it. ON the Massey F40 that I bought last week, the battery keeps running down. Looking at it I find there is 1 wire form the alternator connected to a wire coming to the neutral safety switch. The safety switch is disconnected and these wires are taped together ( I know this is wrong) If my memory serves me correctly, there is the main wire connected to the back and one wire on the top connected while ther other top wire does not go anywhere (Delco alternator} Also if I remember correctly, the main wire on back goes to the amp guage and there is a wire coming off the switch to the safety switch with the other going to the solenoid. This has been talked about several hundred times but like tools, when you need it you can never find it. Somebody please tell me how to wire it up. Keith
 
A 10 gauge wire goes from the big output stud terminal to the load side of the amp gauge. From the other side of the amp gauge a 10 gauge wire should go to a 40 amp fuse link. From the fuse link a 10 gauge wire goes to the battery connection on the starter, or the battery side of the heavy current starter switch. (this leads directly to the battery positive post)
From the #2 spade terminal on the edge of the alt, a 6" long 14 gauge wire is connected to the output stud. (this wire controls output voltage by sampling it at the source.
From the #1 spade terminal, a 14 gauge wire attaches to one of three things: a diode with the marked end toward the alternator, or a 10 ohm 10 watt resistor, or a lightbulb type side marker lamp. Using one of these options prevents the alternator from keeping the engine running. The diod, resistor, or lamp other terminal is then connected to the ignition so that it gets 12v power only when the ignition is on. (if a ignition resistor is used, it should be on the ignition switch side of that resistor, not the coil side.)
If the diode is chosen, it can be found in an old alternator, or from an on line source. it should be able to handle 4 amps, with a 250 PIV rating. Common commodity device.
If a marker lamp is chosen make sure that it is not grounded, the connections are through it, not to ground.
Good luck, it is not hard. Jim
 
Thanks my friend, sometimes this old body and brain just don't seem to work together anymore. With age we seem to forget things if we don't do them every day. Keith
 

Heavy wire to battery. Voltage reference terminal to an always live terminal just prior to the fuses or circuit breakers. The exciter circuit on has power when the machine is running and with a diode or idiot light in the circuit.
 

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