Model M - Electrical problem?

Kris1946A

Member
I believe I have another electrical problem with my 1949 M. It has been starting and running fine. Today, while it was running, I noticed that the ammeter needle wasn't moving and I was worried the battery wasn't charging. I played with the switch from low to high charge, and then turned the switch all the way to the right where it says Lights and Off. The tractor shut right down, now it won't start again.

I've check some connections, and all seemed fine. I tried to see if there was spark on the plugs by holding the plug up against the tractor metal and turning it over, no spark. I see some older posts on here and will start checking where i have power and where I don't. But in the meanitme, does anyone have any ideas? Any reason shutting the tractor down by turning the switch all the way to the right might have done? There are no wired lights on this tractor. There is a stud off the wire harness for lights to plug into. I thought mayde I shorted something out by trying to turn the lights on, but id didn't look like that stud was touching anything. Thanks for any ideas!

Kris
 
I have the same tractor and it would be my guess that the generator isnt genning. Try charging the battery and see if it runs. With battery ignition it will run until the battery gets too low.
 
Thanks for the reply. That was my problem last year. I had the generator rebuilt this winter and until today, the ammeter was showing a charge. The battery is fully charged and has 6-volts on my tester. When I pull the starter knob I have plenty of juice.
 
With a fully charged battery the needle won't move. If it still has the 6v cutout the light switch will change the charge rate.

I would check the inline fuse above the battery first. If it's good something probably happened inside the switch. You can take it apart and clean up the contacts. If you decide to replace it be very careful. Most of the aftermarket ones are sold for an M & a 40 and they won't work on an M. The Deere one is very expensive.
 
M- Man, thank you! I didn't think about the battery not charging if the voltage regulator is working. So it makes sense that the needle wasn't moving if there were 6+ volts on the battery. I did check that fuse earlier and it was blown I had just replaced that fuse a month or two ago bc the battery wasn't charging then. I replaced it with a new fuse and that didn't seem to make a difference. Does that fuse make a difference with the spark? In the diagram I have, it looks like there is a straight shot from the switch to the coil ( the blue wire). I'll have to check that next. I wish it wasn't so hard to get into the dash without taking the gas tank out. Thanks for your help!
cvphoto153005.png
 
Look at the diagram again. Yes the blue is a straight shot from the switch to the coil BUT the wire with the inline fuse powers the switch. No power going in and none will go out.

Yep, it would be nice if it was easier to get to!
 
Kris, good advice from the M Go To Guy, M Man. On those tractors when they fail to charge it can be the switch lacks a good case/frame ground due to rust corrosion bad connections or a bad switch. When running momentarily jump the Gennys FLD post to a good ground.....If it charges then (says genny itself is okay) but NOT otherwise, the switch is bad or not well grounded or the wires open from FLD on genny up to the switch. As the diagram shows if that fuse is bad/open theres no power for loads.

John T
 
Thank you all for your input, especially M-MAN! Based on your advice, I went back to the fuse. The new one I put in yesterday was fine, but as I played around with it, I realized that both ends of the fuse holder were not staying together. When I held them together with one hand, I pulled the starter with the other and she started right up! SO M-MAN - you were right about the fuse. And I'm glad - I was just about to order a $100 switch!

I really can't thank you guys enough. I don't have any friends that share the same hobby and am figuring things out as I go. Without help from this forum over the past couple of years, I would probably have '46 and '49 lawn ornaments instead of tractors! Thanks again!
 
Good to hear and thanks for letting us know!

When I made a new wiring harness for mine I did away with the inline and put in a long lead new type fuse holder from NAPA in its place. It hangs down beside the battery and can be changed in seconds just by opening the door. You might consider that if your holder is bad.
 
M-Man, that is a good idea! I picked up a glass fuse holder so I could replace the one that's on there. But replacing with a new-type fuse makes sense and will be a lot easier in the future. The fuse that was in my tractor when I got it was a 20-amp. Is that what you run? It still has the 6-volt system.
 
FWIW, the fully clockwise position on my '48 is also "OFF" and kills the engine, just like the fully counter-clockwise position. I'm thinking that may be normal.

Look familiar?

http://www.wwdsltd.com/files/1948DeereMConsoleWiring.jpg

1948DeereMConsoleWiring.jpg
 
Hi Watthour, I can't see the photo you posted. But, yes, fully clockwise kills the engine on mine too. I just couldn't get it started
again. After some help from the others that posted - I narrowed it down to a problem with the fuse. I've got that temporarily fixed and I'm
back up and running. Thanks for your response!
 

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