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Discussion Forum

D15 ignition switch

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04-19-2008 12:47:00

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Looking for some help with this one:

I've got a '61 D15 gas that has been converted to 12v neg ground and a Delco 10si alternator added. Starts great but won't shut down when the key is turned to "off." Comparing the wiring to diagrams on this site, the wiring looks right to me, but obviously something isn't right.

Any help would be great.


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04-21-2008 03:28:54

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 Re: D15 ignition switch in reply to Flat47, 04-19-2008 12:47:00  
Texas Denny - Thanks for the input. I went to Radio Shack yesterday to get the diode and they were all out...so this project will be delayed a bit.

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04-20-2008 03:45:43

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 Re: D15 ignition switch in reply to JLM/Minn, 04-19-2008 12:47:00  
Thanks, guys.

There are three connections on the back of the switch: battery, solenoid, and coil. This appears to be the original switch.

I'll try the diode and see what happens.

Thanks again,


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Texas Denny

04-20-2008 06:07:00

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 Re: D15 ignition switch in reply to Flat47, 04-20-2008 03:45:43  
I think you will need one of my three earlier suggestions. The diode is trouble free. It has polarity so it must be installed the correct way. If you install it wrong, the alternator won't work. There is no damage. Hook it up the other way and it should work fine.

There is a possibility that the solenoid connection would work but it is doubtful. Usually when the switch is turned from start to run, the alternator is not spinning fast enough to start.

I have a Ford 901 that I put the normally open switch on. It works fine but sometimes I forget to push it. And occasionally when I idle it down too slow, the alternator drops out. I like the diode option the best.

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04-19-2008 19:37:33

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 Re: D15 ignition switch in reply to Flat47, 04-19-2008 12:47:00  
your ignition switch is a simple off - on switch. It breaks the current going from the battery to the coil. If turning ot switch off doesn't stop the tractor, then you have something connected wrong and power is bypassing the switch. diodes are not needed if wired correctly. Bob

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Texas Denny

04-19-2008 19:57:19

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 Re: D15 ignition switch in reply to chalmersbob, 04-19-2008 19:37:33  
I should have said typical ignition switch. I do not know the number of poles on an original D-15 ignition switch. It may have a separate terminal for the alternator. My D-17 does but the D-14 doesn't.

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Texas Denny

04-19-2008 19:52:39

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 Re: D15 ignition switch in reply to chalmersbob, 04-19-2008 19:37:33  
The standard ignition switch is a two pole switch. If you have a four pole switch which switches the field to the alternator separately from the ignition, you can avoid the second switch or the diode.

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Texas Denny

04-19-2008 15:18:50

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 Re: D15 ignition switch in reply to Flat47, 04-19-2008 12:47:00  
The alternator needs voltage to get started. Once it has been energized it feeds voltage backwards when you turn off the ignition on that energize wire. To correct the problem, put a diode in that line. The diode will let current flow to the alternator to get started but won't let it come back toward the ignition switch to keep it running.

Another alternative is to put a push button switch in the line which is normally open. Push it once after starting the tractor, and the alternator is good. If you put a normally closed switch in the line, push it after turning off the ignition , hold until the engine is stopped and then release. The push buttons serve the same purpose as the diode - provide energizing voltage and current and a way to prevent reverse flow.

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