Help!!! Cuttman

TWheat · Jun 3, 2011

I don't want to hijack Cuttman's topic, But
Jim N said
"An oil pressure switch that is open with no pressure, and closed when under pressure is ideal for this, as it is automatic (NAPA has them).
The wire with diode goes to this new switch ("T"ed into the oil pressure port.) and the switch is supplied with voltage from the starter switch on the hot terminal. A plain SPST toggle switch can be used in place of the oil pressure switch, but it must be turned on manually and off manually each time the tractor is operated."
I haven't been able to get it fixed in my mind how the engine could start if there was no current because the oil pressure switch had the current cut off.
Are you saying that the oil pressure switch is wired to energizing the starter , cranking the engine with the starter, temporarily providing that current until the engine starts and builds oil pressure??
Thanks,
TWheat

Red Dave · Jun 3, 2011

I think he is referring to using the oil pressure switch to control the alternator, keeping it from discharging the battery when the engine is not running.

The oil pressure switch would not have any affect on the start or run circuits.

Jim, I apologize if I have this wrong.

TWheat · Jun 3, 2011

OK, but I guess I need to rephrase it.If the engine shuts off when there is no oil pressure ,
how can you re-start it , as you have no oil pressure to start with. I'm trying to understand how it overcomes cutting it off on one hand and lets it start on the other hand. Guess I'm missing something?

Janicholson · Jun 3, 2011

You didn't hijack anything but an explanation.
The oil pressure switch is used on Magneto equipped tractors to excite the alternator when wiring a Hitachi or Delco10SI alternator.
The ignition is not involved with a mag, as that is a totally discrete system.
On this application, the Diode (when using the oil pressure switch) is not needed, but I was trying to explain an either or situation.
The ignition with a distributor could be wired up the same with an oil pressure switch, but the ignition source and a diode, light, or 10 ohm resistor work as well.
On a Mag, a separate on off switch is used, in addition to the mag kill switch, to activate the alternator if the oil pressure switch is not used.
Even a momentary contact single pole switch can be used to give the alt the signal to charge. Once it is charging, it will stay charging without any more exciting voltage until the tractor is shut off. Jim

Janicholson · Jun 3, 2011

The oil pressure switch is not a part of the ignition system. Only the exciter circuit to the alt #1 pole. See the other answer posted 30 seconds ago, all is well. Jim

Janicholson · Jun 3, 2011

This will help! Jim

TWheat · Jun 3, 2011

Thanks Jim, I understand it now that the oil pressure switch's purpose is not what I thought it is and that it is not a part of the ignition system.

Tim

John M · Jun 3, 2011

I use them on conversion with one wire alts, mag or dist. igniton.

ih560 · Jun 4, 2011

Why would you need to use an oil pressure switch with a one wire alternator? The purpose of a one wire alternator is so that you don't have to hook up a field and sensor wire. They are self exciting, in that, once enough rpms are reached a magnetic field is generated and the alternator begins to charge. If you are still hooking up a field wire on a one wire alternator then you are defeating the purpose. Although, I do prefer a 3 wire, for the purposes of better charging and quicker exciting. I have seen some 1 wire set-ups where the person would have to over-rev the tractor to get it to start charging, which could have been solved with a smaller pulley on the alternator, but it would not even have been an issue with a 3 wire, hooked up correctly.

Janicholson · Jun 5, 2011

If the switch was rated at 50 amps or more, the alternator would be able to run directly to the battery (Through a fuse link if I were doing it)
This would eliminate the constant draw of a One wire system. Some draw such that the battery can be drained to no start, in a month, some are less drain, but more RPM to excite.
If a low amp switch was used, a relay could be used to make it work, but that is more complex than a good to go 3 wire. Jim

John M · Jun 5, 2011

One wire alts have a tendency to drain the battery over time if its not used.

ih560 · Jun 5, 2011

(quoted from post at 17:42:15 06/05/11) One wire alts have a tendency to drain the battery over time if its not used.

So then I assume you are using the oil pressure switch to trigger a conitnuous duty solenoid? A couple of the tractors I have, do have 1 wire alternators, not by my choice, but they were like that when I got them and they have't had any problems yet so I haven't changed them. Only one of those two will run the battery down after a couple of months of sitting, so I just unhook the battery when I know it is going to be sitting for a while and if it hase been sitting for more than a few weeks without starting I will just stick the charger on it, in maintain mode, to bring it back up to full charge.

Help!!! Cuttman

TWheat

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Red Dave

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TWheat

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Janicholson

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Janicholson

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Janicholson

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TWheat

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John M

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ih560

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John M

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ih560

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