JOHN DEERE 50 REWIRED

[lonestar7778]

Hey folks, I been working on a John Deere 50 serial #5033437 this winter. The wiring was a mess and it had a key switch add on. So I have replaced the battery and returned it to a positive ground I also changed ignition switch, ballast resister, coil, points I have also replaced all the wiring on the tractor. The starter works great the light work and amp gauge works but tractor will not start. I have been doing some research on this forum and have been using John T trouble shooting procedure. But he says that I should show 6 volts on meter at the high side of coil with the ignition on. When I put a meter on the high side coil to the negative terminal on the battery I am getting 12 volts but no spark from coil lead. I used the john deere parts catalog to wire the tractor the picture are not great so I think I may have some thing wired wrong. Any ideas or help would be much appreciated. :?

 

[mattroh]

Here's a page from the John Deere Electrical Manual, SM2023

Link:
SM2023 - 50, 60, 70 wiring diagram

Larger Image:
SM2023 - 50, 60, 70 wiring diagram

Hope it helps,
Matt

 

[John T]

In my Troubleshooting Procdure the voltage measurements are measured between the frame Ground and wherever else I'm measuring (such as coil voltage). The voltage should be measured from the coil to the tractors iron frame which, for Pos ground, means the POS BATTERY POST NOTTTTTTTTT THE NEG AS YOU STATED!!!!!!!!!!!

DEFINITION like most others (and as understood by "most" old tractor mechanics and farmers and even us electrical engineers) I refer to the metallic conductive tractor frame as GROUND. The batteries POS terminal is bonded to the tractors iron frame ON WHAT ARE CALLED POSITIVE GROUND TRACTORS. What are commonly referred to (by myself and "most" others) as Neg Ground tractors, the batteries Neg post is bonded to the tractors frame. Most mechanics, engineeres, and tractor manufacturers refer to those old tractors as Pos or Neg grounded based on which (Pos or Neg) battery post is electrically bonded to the tractors iron frame


You say you took it back to Positive Ground so THEREFORE the voltage on the coils high input side (NOT side to distributor) with ignition on and points closed with respect to frame ground WHICH IS THE BATTERIES POS TERMINAL IN THIS CASE NOTTTTTTTTTT ITS NEG TERMINAL would be 6 volts because the external series voltage dropping (12 to 6) ballast resistor drops 6 volts leaving 6 on the high input coil terminal

Take a voltmeter and place it on the coils high input (NOT to distributor) terminal with the other meter lead to the frame ground (nice clean shiny conductive part or even on the batteries POS (to frame ground) post and insure the points are closed and turn the ign swith on and you should read around 6 volts if all is correct and wired right......

EASIER TEST: (No polarity worries)

Take a 6/12 test lamp with one lead to frame ground,,,,,,,,,,,turn ignition ON,,,,,,,,Put other lead on the high input (NOT to distributor) coil terminal IT HAS TO LIGHT UP OR SHES NEVER GONNA FIRE,,,,,THERE MUST BE COIL VOLTAGE TO WORK

Okay if it lights up leave the one test lamp lead to frame ground and put the other lead over on the coils low to distributor terminal,,,,,,turn it on and crank it over,,,,the light should flash ON and OFF, its ON if points are open but OFF if they are closed

Shes NEVER gonna fire until the coils high input (From switch and ballast NOT to distributor) has voltage (with respect to frame ground) and theres a conductive path to frame ground via the points which open and close to allow and interrupt coil current flow

PUT A TEST LAMP ON THE COILS HIGH INPUT (NOT to distributor) AND IT BETTER LIGHT UP when ign is ON

If notttttttt insure current path wiring out of Ign switches IGN terminal,,,,(need voltage there when ON),,,,,,,,,,,to and through the ballast resistor,,,,,,,,,,to and through the coil,,,,,,,to and through the points when closed,,,,,,to and through the tractors conductive iron frame ground,,,,,,,to the grounded battery post

NOW ARMED WITH THIS and aware voltage is measured between the item and frame ground

CHECK THE WIRING AND RE WORK MY TROUBLESHOOTING PROCEDURE BELOW

John T

John Ts Ignition Troubleshooting

 

[John T PS]

PS the coil wiring on those can be confusing for lay persons, it isnt for the timid lol

I SUSPECT YOURE NOT WIRED RIGHT AND YOU ARE LACKING COIL INPUT VOLTAGE

The coil may have 3 or 4 wires on it.

On the high input (NOT to distributor) one wire from the switch and ballast and another from the tractors starter switch (ballast by pass circuit) althoug the ballast by pass can be wired to the ballast resistor instead.

On the low output (To distributor NOT from switch/ballast) theres a wire to the distributor plus can be another to the switch.

For a Pos ground tractor (means battery POS is tied to frame ground for the rookies) the coils - is wired to the switch/ballast while its Pos wires to the distributor

CHECK THE WIRING AND INSURE COIL HAS VOLTAGE ON ITS INPUT WHEN IGN SWITCH IS ON

John T Takin the "first wife" out for a Valentines Dinner, will check back later

 

[lonestar7778]

Hey John T thank you for the great information. I will keep you update next week when I get back out to the farm to work on the tractor. Just from your information I think I may have the ground and the battery wire on the back of the switch mixed up. I will also get some new battery cable so I can move the ground from the battery box down to the frame.

 

[John T]

A good shiny stainless steel bolt with star lock washers direct to a heavy frame member often makes a better frame ground contact versus thin wimpy (especially if rusty) seat box sheet metal.

Post back any questions when the time comes and I know that diagram is hard to see and follow

John T

 

[lonestar7778]

Well I got back out to the farm and got to work on the JD50, I installed new battery cable and moved a few wires that I had wired wrong. I got the tractor to start but could not get it to run more than a minute or so. I've been having a problem with the two 6volt battery and was going to change to single 12 volt battery, I usually shop Autozone so any suggestion on size and cranking amp for a new battery. I took that carburetor off to rebuild it and I was wondering if there are any checks I need to do on the carburetor before I re install it. Thanks for all the help.