Diode or relay?

Tractorcedric · Dec 3, 2020

So I have replaced a F162 Continental with a F163 out of an air compressor. It came with a 12 volt setup. There was a ballast resistor by the coil. My key switch only has a on/off position, no start or accessory. Is there a diode I could get that I could put in a smaller wire from the old foot starter to the coil to give the coil a full twelve volts when cranking. What diode would I need? I could use a relay but that is a lot more wiring! I am a big fan of the KISS principle. Oh this is in a Massey Harris 101 Jr. It also came with a 10D alternator with an external regulator if that helps.

Jim.ME · Dec 3, 2020

(quoted from post at 13:15:18 12/03/20) So I have replaced a F162 Continental with a F163 out of an air compressor. It came with a 12 volt setup. There was a ballast resistor by the coil. My key switch only has a on/off position, no start or accessory. Is there a diode I could get that I could put in a smaller wire from the old foot starter to the coil to give the coil a full twelve volts when cranking. What diode would I need? I could use a relay but that is a lot more wiring! I am a big fan of the KISS principle. Oh this is in a Massey Harris 101 Jr. It also came with a 10D alternator with an external regulator if that helps.

KISS = Try it without a bypass, it likely doesn't need one. I've got several units that use a ballast resistor and they don't have bypass wires, no issues with starting.

fixerupper · Dec 3, 2020

Like Jim Said. If you are starting this engine in the winter you might want the bypass wire but that can be added later. It all depends on how well the engine starts.

Duner Wi · Dec 3, 2020

I have used # 276-1144 from Radio Shack.
I know for certain it helps lots under the right conditions.

wore out · Dec 3, 2020

Some guys have used diodes as you describe, trouble is they have a "forward voltage drop" of about 0.6 Volts, so you lose that much voltage vs. a relay. A little 10 Amp diode would be more than adequate for the job, one industry number is "10A10A".

Another option would be to install a simple pushbutton switch that you could hold in during cranking to bypass the resistor.

Tony in SD · Dec 3, 2020

pete 23 · Dec 3, 2020

You can use a diode no problem to get higher voltage to coil for starting BUT remember. It is not going through the ign switch so any time you kick that starter switch, engine will fire up until you let go of starter. Dangerous.

cuby · Dec 3, 2020

I make my own diode by taking them from a 10si Delco alt. Work super for me.

Tractorcedric · Dec 3, 2020

I had not thought of that!!

Tractorcedric · Dec 3, 2020

Now your talking!

Janicholson · Dec 3, 2020

You could put a switch in that wire with the diode, to allow start free cranking. The systems now in place from the factory don't have a switch, and can start when cranked, but 99.9 times that is the intent. Jim

David G · Dec 3, 2020

I would just wait to see if you need it.

Diode or relay?

Tractorcedric

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Jim.ME

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fixerupper

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Duner Wi

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wore out

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Tony in SD

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pete 23

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cuby

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Tractorcedric

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Tractorcedric

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Janicholson

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David G

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