The 12 volt electrical on my 400 was in really bad shape when I got it so I went ahead and rewired the tractor completely. New wiring, gauges, and a new GM 1 wire alternator. I followed wiring diagrams and everything is as it should be except that my gauge shows the alternator to be discharging while running. I know that I could have the wiring switched around on the gauge, but how can I check the alternator to make sure it actually is charging?
- Thread starter TXZane
- Start date
Janicholson
Well-known Member
At 3/4 throttle there should be 14.2 to 14.7 volts across the battery. If there is, it is working.
If your "one Wire" is connected to the starter relay (solenoid) BAT terminal, the amp gauge will never show charge. If that "one Wire" is connected to the load side of the amp meter it will show correctly Charge when it is, then usually go back to the middle in a few minutes (it is still charging!) If the lights are turned on when the tractor is stopped, the gauge should move to discharge. If it shows charge at that point the gauge is backwards. Jim
If your "one Wire" is connected to the starter relay (solenoid) BAT terminal, the amp gauge will never show charge. If that "one Wire" is connected to the load side of the amp meter it will show correctly Charge when it is, then usually go back to the middle in a few minutes (it is still charging!) If the lights are turned on when the tractor is stopped, the gauge should move to discharge. If it shows charge at that point the gauge is backwards. Jim
A quick check to tell if the alternator is charging is to check to see if there is magnetism by holding a small screwdriver to the rear bearing of the alternator when the engine is running at half throttle. The magnetism should be strong enought to hold the screwdriver. I will also add what Jim suggested is the best, "Use a voltmeter" The magnetism check is just a quick check.
Phil Tibbetts
Well-known Member
Just an idea but the 1 wire Alternator on my 364 won't start charging until I rev the engine up to nearly full throttle. Once it starts charging I can cut the throttle back to idle and it will still charge until I shut the tractor off.
First, electrical is a big mystery to me.
Second, charlieu sells / sold a little diode to me a year or two ago, that plugs right into the top of that alternator, and makes it really charge immediately on startup, then tapers off. Very econmiical. Economicaxl. Well, you get the idea.
Second, charlieu sells / sold a little diode to me a year or two ago, that plugs right into the top of that alternator, and makes it really charge immediately on startup, then tapers off. Very econmiical. Economicaxl. Well, you get the idea.
Here's another test that doesn't even require any wiring knowledge or even starting the tractor:
Turn on the ignition and observe which way the needle moves. It should move slightly to the left, indicating a slight discharge.
You could also turn the headlights on to get a more significant discharge.
If the needle moves to the right, then you have the ammeter wired up backwards.
Turn on the ignition and observe which way the needle moves. It should move slightly to the left, indicating a slight discharge.
You could also turn the headlights on to get a more significant discharge.
If the needle moves to the right, then you have the ammeter wired up backwards.
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