Mf 150 fried ammeter wire

[jleonardwv]

This is the first day I've had my Massey Ferguson 150 out for a test run since I bought it in December. I had hooked up a new ammeter in what I thought was the exact same configuration of the one I removed which was not working. After examining the tractor a half hour or so after running around the field, I see that the wires, both of them leading from and to the ammeter got so hot and it burned off the insulation all the way up and down. Any suggestions what I did wrong?

 

[jleonardwv]

 

[jleonardwv]

The one time I did look at the ammeter while driving, I noticed it was negative 30. I assume that's not normal.

 

[rvirgil_KS]

The ammeter often mounts with the 2 posts going through a horse shoe shaped bracket. The bracket is grounded to the tractor frame. The posts must be isolated from the bracket, usually by a rubber or fiber grommet. Make sure that the ammeter posts are not shorted to mounting bracket, or that wire is pinched somewhere

 

[4play]

Looks like you let all the smoke out. What size wire was that, and what kind of electrical loads were you using? Too late now but if doing an ammeter again, put a fuse in the circuit for the rating the wire can handle? IMO ammeters (unless inductive type ) are not worth using, mainly for reasons like this.

Insufficient wire gauge, additional electrical loads, bad connections, poor insulation or short to ground are all bad scenarios for ammeter wiring.

 

[ptfarmer]

Put a volt gauge in it, it's better, and much safer.

 

[CitrusGrower]

-30A continuously is definitely not normal. You should have a small positive number indicating the alternator is continuously charging the battery, even if the battery is fully charged.

Even if your alternator is doing nothing I wouldn't expect the drain to be -30A unless you have all kinds of lights and a big sound system.

30A continuous calls for 8 AWG wire, and shouldn't be happening. Find the 30A drain first, then worry about whether you need heavier wires for your ammeter.

 

[jleonardwv]

Unhooked the ammeter entirely. Ran new wires from regulator to generator.

Threw away the wire from the ammeter to the starter. Did not replace. Threw away the wire from the regulator to the ammeter. Did not replace.

Now it won't start. Did I fry something else? Battery shows charge and even with jumper cables from my van, nothing at all when I turn the key.

Shows 12v on the battery. Shows 12v at the starter. 12v at the soleniod.

 

[rvirgil_KS]

"Threw away the wire from the ammeter to the starter. Did not replace." You must have this wire to feed charge current down to the battery and to feed battery current back up to the switch for starting

"Threw away the wire from the regulator to the ammeter. Did not replace." You must have this wire to feed generator charge current to ammeter and on to battery. Also to power the L terminal on regulator (if it has one) which powers the light switch

The ignition switch will receive power either from one side of the ammeter or from L terminal on regulator

"even with jumper cables from my van, nothing at all when I turn the key." Ignition/start switch is not getting power


You must have those two wires to connect the charging system and power the switch.

 

[jleonardwv]

Ran a wire from the starter to the voltage regulator, bypassing the ammeter, and it works!

Thanks for the helpful suggestions.