400D Wiring Issue

Posted by David Bean on September 22, 2002 at 21:22:03 from (67.225.130.11):

Hi all,

I've been working on a restoration of a 400D, and a couple of weekends ago I ran into an electrical problem. Specifically, I replaced the hodge-podge of wiring that was on the tractor with a brand new wiring harness. But, when I tried to start the motor, I cooked one of the wires. It's clear that it was just getting a full flow of 12V -- within a few seconds it was hot enough to melt the insulation all along its length.

The wire in question ran from the IGN connection on the ignition switch to the manifold switch -- a black wire if you follow the colors of wiring diagram in the manual.

Now here's the interesting part: when I got the tractor a few months ago, it was running, but the wiring didn't match up with the manual's wiring diagram. Before I pulled all the old wiring off in June, I made some notes about how it was laid out. But when I put the new harness on the other day, I put it on according to the manual, *not* according to how it was when I got it.

Initially, I thought there was a lot of difference between the two wiring setups, but after I drew them both out on paper, I saw that there was only one minor difference. On the setup that worked a few months ago, the black wiring ran from the ignition switch's IGN connection to the top of the coil. So, the manifold switch was just out of the picture entirely. In the by-the-book setup, the black wire runs from IGN to the manifold switch and there's a small jumper wire from the other side of the manifold switch to the coil.

So, the only difference is the manifold switch between IGN and the coil.

Now, given the behavior of the cooked wire, I'm thinking that the manifold switch is messed up in some way. It seems to me that the manifold is acting as a ground, so when I turn the switch to the ignition position, it allows a complete circuit from the generator through the regulator to ground.

I'm not sure what a manifold switch is. On my 400D, it looks like two simple studs set into the end of the manifold. Should there be any sort of connection between the two studs? Does it have any necessary function, or is it like an appendix -- something I can bypass without worry?

I've posted my wiring diagrams to the web in case my description doesn't make sense. If I do this right, the address should show up below...

I welcome any thoughts or comments.

Thanks!

- David

• Wiring diagrams

Follow Ups:

• Re: 400D Wiring Issue Sven 07:27:20 09/23/02 (0)
• Re: 400D Wiring Issue Bob M 07:24:35 09/23/02 (1)
  • Re: Re: 400D Wiring Issue David Bean 15:34:28 09/23/02 (0)

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