John Deere 620 Issues with Electric System

mrgooddeeds · Aug 13, 2019

I apologize if this is not the correct board to post this on. I m new to this site and I know little about tractors. But my father owns a 1958 John Deere 620 and he is currently at his wits end trying to get it to run. He isn t the most tech savvy person so I m asking this on his behalf. He recently switched the generator out for an alternator and was able to start it up and drive it for 10 minutes afterwards. After that he has been able to start it twice but only for 4 or 5 seconds before it dies, then after that he has been unable to get it to start. He has replaced the main battery cable, condenser, switch, resister, points, resister (on the distributer), rotor cap, distributer cap, spark plugs, and the coil. (He has replaced the coil with a hot spark coil and also tried to replace it with a standard coil, and neither has worked. And he has tried to replace the electronic ignition in the distributer but it didn t work so he switched it back.) (I think he has replaced most of the wires with what looks like 16 gauge wire.)

Right now when you put a screw driver to the terminals on the coil and touch metal you get a spark for each terminal. When you try to start the tractor and you hold the coil wire there is no spark coming out of the coil wire. (I only know this from holding the wire end when there is an attempt to start the tractor.)

Also not sure if it matters but the tractor is running 12 volt battery as opposed to the dual 6 volt setup the tractor had in the beginning. (This was replaced long ago and has worked fine since.) The battery has been fully charged as well.

He has done everything that he can think of at this point. If anyone has any thoughts as to why this tractor isn t starting, we would greatly appreciate it if you shared them.

Thanks,

Bob · Aug 13, 2019

"when you put a screw driver to the terminals on the coil and touch metal you get a spark for each terminal"

Are breaker points installed now?

If so, when the breaker points are CLOSED, they short one side of the coil primary to ground, and it is at the instant that the points OPEN that spark occurs.

So, back to your screwdriver test... if the engine has stopped with the points closed you should NOT have voltage on both coil primary terminals. If you rotate the crankshaft enough to OPEN the breaker points, then both primary terminals will hace power.

Try this... connect a non-powered 12 Volt test light between the distributor-side coil primary terminal and ground and crank the engine (with ignition "ON").

Light should flash ON when points open, then go out while points are closed.

If it doesn't you have dirty or mis-adjusted breaker points or a bad connection in the primary circuit.

Give the test light thing a try and let us know what you find!

buickanddeere · Aug 13, 2019

This is a regularly appearing problem after somebody "improves " their tractor . Alternator is wired incorrectly and is draining the battery . Less troubles with the factory 20amp Delco generator .
The wiring harness is possibly all
Mixed up and moved around . There is a wiring diagram in the factory service manual for electrical systems .

John T · Aug 13, 2019

Since this question gets asked a gazillion times I have an Ignition Troubleshooting Procedure which can help find the problem.

See if it helps and post back any questions

http://www.ytmag.com/cgi-bin/viewit.cgi?bd=farmall&th=5745

John T
John Ts Ignition Troubleshooting

buickanddeere · Aug 13, 2019

(quoted from post at 12:11:38 08/13/19) I apologize if this is not the correct board to post this on. I m new to this site and I know little about tractors. But my father owns a 1958 John Deere 620 and he is currently at his wits end trying to get it to run. He isn t the most tech savvy person so I m asking this on his behalf. He recently switched the generator out for an alternator and was able to start it up and drive it for 10 minutes afterwards. After that he has been able to start it twice but only for 4 or 5 seconds before it dies, then after that he has been unable to get it to start. He has replaced the main battery cable, condenser, switch, resister, points, resister (on the distributer), rotor cap, distributer cap, spark plugs, and the coil. (He has replaced the coil with a hot spark coil and also tried to replace it with a standard coil, and neither has worked. And he has tried to replace the electronic ignition in the distributer but it didn t work so he switched it back.) (I think he has replaced most of the wires with what looks like 16 gauge wire.)

Right now when you put a screw driver to the terminals on the coil and touch metal you get a spark for each terminal. When you try to start the tractor and you hold the coil wire there is no spark coming out of the coil wire. (I only know this from holding the wire end when there is an attempt to start the tractor.)

Also not sure if it matters but the tractor is running 12 volt battery as opposed to the dual 6 volt setup the tractor had in the beginning. (This was replaced long ago and has worked fine since.) The battery has been fully charged as well.

He has done everything that he can think of at this point. If anyone has any thoughts as to why this tractor isn t starting, we would greatly appreciate it if you shared them.

Thanks,

Sometimes after 60 years of use, rodents , vibration, mud, manure , various mechanics tinkering . Sometimes it is simpler, safer and cheaper to obtain a replacement wiring harness from https://www.wiringharnesses.com/

mrgooddeeds · Aug 13, 2019

I guess I should have thought to search for commonly asked issues. Thanks for pointing the ignition troubleshooting guide out.

mrgooddeeds · Aug 13, 2019

I suggested that this issue is linked to the alternator but my father insists that it is not. I can't really argue against it because of my
lack of knowledge on the subject. Could just having the alternator as opposed to a generator hooked up; be lowering the voltage enough to not
to get a good spark out of the coil? I believe that when he first replaced the alternator and got the tractor to run, he had just put in a
freshly charged battery. The battery has a decent charge now but maybe the battery needed to be at a minimum of a full charge to barely
start. (Sorry I know nothing about engines.) I'm not sure if what I'm thinking is even the way this works. Anyways thanks for your response.

mrgooddeeds · Aug 13, 2019

I'll mention this. I'm sure it wouldn't hurt if it was replaced. Thanks.

mrgooddeeds · Aug 13, 2019

This is something that I will make sure we go over the next time we work on the tractor. Might have some followup questions on this once I speak to my dad. Thanks for the response.

buickanddeere · Aug 14, 2019

It is possible the alternator has been blown up internally by being connected reverse polarity .
Is this an ordinary one wire or three wire alternator ? What is the coil polarity and what is the battery polarity ?

John Deere 620 Issues with Electric System

mrgooddeeds

New User

Bob

Well-known Member

buickanddeere

Well-known Member

John T

Well-known Member

buickanddeere

Well-known Member

mrgooddeeds

New User

mrgooddeeds

New User

mrgooddeeds

New User

mrgooddeeds

New User

buickanddeere

Well-known Member

Similar threads