M Electrical

[Renglund]

My father-in-law gave me a Farmall M circa 1949 model. The electrical system has been converted to a 12 volt system.

The battery doesn"t seem to be holding a charge and the ampmeter shows discharge.

It was hooked up negative ground when I got it and he had put a new battery in it.

Could this be a positive ground system and I need to reverse the battery cables?

 

[RobMD]

Is it an alternator system? Well, then it's definitely going to be a negative ground system. Sounds like the alternator is shot based on your description; providing that the battery is newer, there are no shorts, and the cables are in great condition.

 

[old]

First thing to do is see if it has an alternator or a genny on it. If its an alternator which it most likely is if you hook it up wrong you will smoke it before you get your hand off the cables. Best thing to do would be to pull the alternator off and have it checked. Most auto parts stores will check them for free, then go form there
Hobby farm

 

[John T]

Is it an alternator or a generator?????? Most all alternators are negative ground

If a generator it can still charge at either polarity fine porvided the genny was polarized and the VR is compatible for that ground. One has to swap coil and ammeter polarity if changing grounds also.

If its a generator I can post my Troubleshooting Procdure to diagnose the problem, let us know.

John T

 

[Gerry....WI]

Reverse the wiring of the ammeter

Check the voltage at the battery with multimeter

 

[onefarmer]

Everything the others have said about the charging system and polarity.

And to check if the ammeter is hooked up correct. Without starting it turn on the lights and/or ign switch if battery ign, and observe if the ammeter shows + or -, If - it is correct if it shows +, then reverse the leads on it

 

[Renglund]

Thanks, all. I"ll try to get out to the farm this weekend and check to see if alternator or generator.

Only gonna be about 24 degrees tomorrow so I"ll get it into the shop to work on it.

Thanks to all of you for all of the advice.

 

[flashback]

My battery kept going down but it was the starter button shorting out just a little bit.Replaced switch and no more problems. At most auto stores or Walmart you can buy a battery disconnect for 2-3 bucks so when left unattended that wont happen