MF 165 Diesel Alternator wiring?

I have a 165 diesel that had been converted to an alternator prior to my purchase. It has a GM 3 wire alternator with a built in regulator. I've tested it at the large post and it is working but must not be wired properly because the battery runs down. The only gauge that appears to work is the temp gauge and tach. It has a two wire push button ignition switch. Anybody help me wire this to charge the system? I'm open to replacing the oil pressure and ammeter, or should I install a voltmeter? I've searched and searched but can't find my identical situation. From what I've seen the wiring is different ammeter vs voltmeter and gas vs diesel and wiring the exciter wire. HELP! Thanks Also, how do I get the ammeter out of the dash?

(quoted from post at 18:54:23 04/05/21) I have a 165 diesel that had been converted to an alternator prior to my purchase. It has a GM 3 wire alternator with a built in regulator. I've tested it at the large post and it is working but must not be wired properly because the battery runs down. The only gauge that appears to work is the temp gauge and tach. It has a two wire push button ignition switch. Anybody help me wire this to charge the system? I'm open to replacing the oil pressure and ammeter, or should I install a voltmeter? I've searched and searched but can't find my identical situation. From what I've seen the wiring is different ammeter vs voltmeter and gas vs diesel and wiring the exciter wire. HELP! Thanks Also, how do I get the ammeter out of the dash?

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f no one comes up with 165 diagrams, I have 135 & 275 and might be same or close???

number 2 terminal connects to 12 volts, usally right back on alternator big post, or at big starter post or ignition switch feed. Number 2 has to be fed by a idiot light or diode, then a switch, then finally to the 12 volts.On my 165,there is a engine oilpressure activated switch that feeds the idiot light and gauges. This way, power get removed when engine is shut off.

Did you check the diodes in it? Could have one blown. They're supposed to act like check valves.

The #1 is the excite wire and you use a diode or light bulb in that wire. I don't think you noticed your typo

If you suspect the alternator is running the battery down, disconnect one battery terminal, connect an incandescent 12v test light in series between the battery post and the disconnected battery cable.

If the light burns bright, there is a drain. If the light does not burn or burns very dimly, there is no drain or such a small drain it would take months to discharge.

If there is a bright light, unplug the alternator harness connector, see if the light goes off.

If yes, reconnect the battery, test the #1 harness terminal. With the switch off there should be no light. If the #1 has power with everything off, the wire is connected wrong. It should be on a switched circuit.

If the light remains on, remove the BAT wire from the alternator. If that kills the light, the alternator has diode problems and will need to be repaired or replaced.

If the light remains on with the alternator out of circuit, there is something else draining the battery. Start disconnecting accessories until the light goes off.

As for the difference in the amp meter wiring and a volt meter, they wire totally differently. An amp meter will have 2 large terminals on back. To remove it the wires will need to be removed and all tied securely together. This is a high amp connection and must be done correctly. You can use a short bolt and nut, and the connection must be tight, and well insulated. Tape alone is not enough, it needs liquid tape, heavy wrap of good electric tape and finally shrink tube.

To connect a volt meter, it simply connects to a switched circuit. Being a diesel it may not have a switched circuit. You can add a switch which would require you to remember to turn it off, or add a normally open oil pressure switch to power the volt meter (and the #1 alternator terminal too!)

Once the wires are removed from the amp meter, there will be a bail running across the back that is held with 2 nuts, remove the nuts, the bail will come off, the gauge will come out the front.

Clear as mud? Take it one step at a time, it's not that difficult!

sounds like your alternator is staying excited which will kill the battery overnight, on a 165 there is a tee below the oil pressure gauge with a pressure activated 2 prong switch which switches the gauges and alternator on and off. There is a small diode in the the wire going to the alternator to prevent back feed the gauges when the engine is shut off. To check this with the engine off unplug the 2 wire connector from the alternator, the # 1 regulator wire shouldn't have any voltage, if you do that is causing the alternator to stay excited, start the engine and it should have voltage to excite the alternator, to check the diode if it's still in the system, and you have voltage with the engine running, the alternator hooked up shut the engine off and watch to see that the gauges switch off when the oil pressure goes to 0 if not the diode is missing there by causing a drain on the battery keeping the gauges hot. MAKE SURE you are working on a 3 wire set-up they can look identical, personally I don't like a care for the 1 wire system because of pass issues with them, if it has a one wire alternator please disregard the information above.

Well, upon further investigation, my alternator is not charging. I believe I may have been getting a reading from the battery or it quit working. I was testing off the big post on the back of the alternator, but now I get 1.04. So since I have to replace it is it best to go with the 1 wire or 3? Any advantages or disadvantages?

(quoted from post at 12:28:39 04/06/21) Well, upon further investigation, my alternator is not charging. I believe I may have been getting a reading from the battery or it quit working. I was testing off the big post on the back of the alternator, but now I get 1.04. So since I have to replace it is it best to go with the 1 wire or 3? Any advantages or disadvantages?

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f you don't have #1 & #2 connected properly, you won't get output

Wow, thanks for the advice. Appreciate your time for the detailed response.