M120 Parasitic Battery Drain - Alternator

[internetgardener]

Hey Everyone,

My 2002 M120 has been draining the battery - I believe it charging the batter but if I let the tractor sit for several days - the battery is dead!

After grabbing my AMP meter today, I found a couple of substantial drains on the battery. The first one was the the back up light, inside light, fuse. Still not sure what the problem is here ... as I haven't gotten that deep into it. But I pulled that fuse and saw a pretty good drop in the AMPs being pulled.

But even after I found that one, there was still a fairly substantial AMP drain. After pulling all the other fuses one by one there was no change - so for sh*ts and giggles I pulled ground off of the Alternator and my AMP drain went to zero!

Should the alternator pull Amperage when the tractor is sitting idle? Any ideas why this would happen?

I don't want to just go replacing the alternator until I have enough information to say it should or should not be pulling any amperage when idle. Or what that amperage should be. Are there any other tests I can perform?

Thanks in advance for any help.

C

 

[100 td]

Faulty diodes in the alternator by the sounds of it, pull it and get it tested, if it's drawing power when everything is off.

 

[85Hokie]

Faulty diodes in the alternator by the sounds of it, pull it and get it tested, if it's drawing power when everything is off.

Excellent point. And very true. However, it can still test and output 12+ volts. Sometimes testing will show it putting OUT voltage - but most mechanics will not test the the slight amp draw sitting idle. You can pull it and place your amp meter in series with it, and show him that! IF that is the case.

 

[100 td]

if it's drawing power when everything is off.

Get it tested for the above, not it's output

 

[Tooljunkie]

Looks like you did all the hard work. The amount of draw for the interior light and backup light would help, but if alt is drawing with key off, its bad.
I have seen a few fords drain with key off.
Twice i had chrysler vans drain battery when temp outside went a few degrees below freezing. Drove me crazy trying to diagnose.