Electrical problem

[trillium33]

I have a John Deere Model 40 that hasn't been started for over 30 years. I have replaced all distrb components and rebuilt carb. I connected the battery and when I turn the ignition switch to start the charge gauge pins instantly to dicharge and the fuse blows. I have taken the switch out and taken it apart and there is no obvious problem. I took the cover off the regulator and saw no obvious problem there either. I cleaned both and tried again with the same result. I bought a new regulator and the same thing. I am baffled why this is happening. I'm hoping someone can help or suggest a next step. The harness look ok and the only other thing I haven't checked is there is a low level oil switch, at least I think that is what it is.
Thanks for any help.
Dave

 

[lwalsh]

These are 6 volt systems? Does the motor turn freely?

 

[BRBurns]

Does the starter turn, or do you hear it engaging the flywheel? If the starter is engaging the flywheel but not able to turn because the engine will not turn, it will draw too many amps. The starter could be lshorted also. Disconnect the hot wire to the starter and tape the end, then try. If nothing blowes, it's you starter or the engine will not turn over.

 

[trillium33]

Thanks for the help. Yes the engine rolls over fine the starter engages like its suppose to. I can connect the battery and pull the starter lever and it rolls over fine. When I turn the key switch to start, the amp meter pins hard discharge. It should only move a little bit to show the switch is drawing a bit of amperes.

 

[BRBurns]

You have the key in the Start position for this to happen, or in the Run position? If in the start position then maybe a bad starter relay.

 

[atschirner]

If this is a stupid question I appoligze in advance but, is this tractor positive ground and is that the connection you are making from the battery to the tractor?

 

[trillium33]

Yes it is positive ground and thats the way I have it hooked up. I even tried switching it to neg ground cautiously and when I turn the switch the amp meter pinned to the positve side instead of the neg side.
There is no such thing as a stupid question and I appreciate your question which if I didn't know it was pos ground would have been a great question.

Thanks again,
Dave

 

[atschirner]

Thanks for your reply and kind words Dave.

Give this a try; connect a sealed beam headlight in series with the negative lead of the battery, it should not glow but with the indications of a hard short, it will. This series resistance / indicator will let you troubleshoot the wiring harness without blowing fuses. It seems counter intutitive but when the key is on and the headlight is not glowing you have located the short. I'll go out on a limb and suggest that a furry little rodent may have dined on your harness at some time in the past. Do you know why the tractor was parked? Are you picking up on the troubleshooting where someone left off?

Have a safe weekend and please let us know what you find.