oil pressure switch in Commando electrical system

This may sound like a dumb question, but can you produce enough oil pressure when kick starting a bike to close a pressure switch, especially when the engine is hot and the oil is thin? There will be no spark until the pressure switch is closed, is that my understanding? Doesn't sound like a one kick and your running scenario.
Texas, good idea. Your diagram will prevent the bike from shutting down when the oil pressure drops.

Deets55 said:

This may sound like a dumb question, but can you produce enough oil pressure when kick starting a bike to close a pressure switch, especially when the engine is hot and the oil is thin? There will be no spark until the pressure switch is closed, is that my understanding? Doesn't sound like a one kick and your running scenario.

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oil-pressure-switch-commando-electrical-system-t19842.html#p254725

xbskt said:

I want to put everything except ignition on the load side of a relay that is controlled by an oil pressure switch

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Slightly off topic, but related. When I converted my commando to negative ground there was no longer any thing to drive the red warning light as its signal came from the warning light assimilator. Instead, I added an oil pressure switch to the rocker feed oil line circuit and drove the light off the switch. From an operational perspective for the light, its exactly like it was before. Both oil pressure & voltage from the alternator/ rectifier are rpm dependent (no battery in older system). It even flickers now and then at low low rpms. It's not as good as a gage, but it's better than nothing. A little more obvious you have a problem too with that red light glaring at you.

Regards,

Don

dgraham42 said:

Slightly off topic, but related. When I converted my commando to negative ground there was no longer any thing to drive the red warning light as its signal came from the warning light assimilator. Instead, I added an oil pressure switch to the rocker feed oil line circuit and drove the light off the switch. From an operational perspective for the light, its exactly like it was before. Both oil pressure & voltage from the alternator/ rectifier are rpm dependent (no battery in older system). It even flickers now and then at low low rpms. It's not as good as a gage, but it's better than nothing. A little more obvious you have a problem too with that red light glaring at you.

Regards,

Don

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I like it. :idea:

A couple of good kicks will extinguish the oil pressure light on my Triumph t140. Same on the BSA Thunderbolt.

L.A.B.

I read that line yesterday, long term loss of short term memory acting up again. Just out of curiosity, when ignition switch is in run position (no lights) the only other load would be brake and turn signals or is it just the MKIII's that have a run /lights off position. The MKIII is the only Norton I am really familiar with, so this question is for general knowledge, to be filed away somewhere.

Thanks,
Pete

You could put in a Murphy Switch-gauge. The switch is actually in the gauge! I have the 117 module that allows starting with no oil pressure and then gives command back to the switch when you let up the button.

http://www.ebay.com/itm/MURPHY-SWITCH-G ... 2c8730bda3

One question I have is: Why kill all the electrics if you loose oil pressure unless you are going to kill the engine as well? I did see the diagram by Slick where it just pulls in and latches when the pressure comes up. That makes some sense since your lights and stuff would not come on if you didn't have pressure after start up.

To me it would just make more sense to have the bike wired to where the engine would only run if it had oil pressure. That way at least you would have lights enough to come to a stop at night if you lost pressure.

Dan.

motorson said:

You could put in a Murphy Switch-gauge. The switch is actually in the gauge! I have the 117 module that allows starting with no oil pressure and then gives command back to the switch when you let up the button.

http://www.ebay.com/itm/MURPHY-SWITCH-G ... 2c8730bda3

One question I have is: Why kill all the electrics if you loose oil pressure unless you are going to kill the engine as well? I did see the diagram by Slick where it just pulls in and latches when the pressure comes up. That makes some sense since your lights and stuff would not come on if you didn't have pressure after start up.

To me it would just make more sense to have the bike wired to where the engine would only run if it had oil pressure. That way at least you would have lights enough to come to a stop at night if you lost pressure.

Dan.

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This relay latch does NOT kill the electrics if oil pressure drops allowing the pressure switch to open. That is the entire point of the circuit. Should the pressure switch open, as it might when idling with hot oil, the latch keeps the lights up until the key switch is turned off. The tendency for the pressure switch to open at idle is why you would not want to wire the bike to quit running based on the pressure switch signal.

BTW....some have reported that Triump and BSA pressure switches are sensitive enough to flick the oil pressure light when kicking over. Such a super-sensitive switch would defeat the intended purpose of this latch, which is to keep the lights OFF until oil pressure comes up with a running engine, and then to keep the lights bright if oil pressure falls below the pressure switch threshold. On the other hand, a super-sensitive pressure switch might obviate the need for the latch if it does not drop out at idle with hot oil.

Slick

Deets55 said:

Just out of curiosity, when ignition switch is in run position (no lights) the only other load would be brake and turn signals or is it just the MKIII's that have a run /lights off position.

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The same basic switch (in either three, or, mostly 4 terminal form) was used for all Commandos from 1971. When the switch is set to 'run' then, unless the brake light or turn signals were actually operating, the only drain on the standard system, apart from ignition, would be the charge warning light (and neutral light, MkIII).

L.A.B.

Thanks for the information

Pete

Just to clarify.
My whole concept is to have only power to the ignition circuit until the bike is running and then the OP switch and relay call in the rest of the electrics. Max power to the coils for startup.
Shutting down the bike for lack of oil pressure was not my intended goal but could be done I suppose with a little tweaking of the diagram and a higher OP threshold. My shovel head would probably never run given the 0 lbs. pressure it shows after the 50 weight sees motion.
I like the latch concept to avoid the lights flashing like a Police bike in stop and go. The relay will most likely be the cube type off the parts store spinner with prewire pigtails and if I remember right rated for 30 amperes. Can't remember right now if they are double pole but that is just details needed to work out. If the relay has a NC contact I may run it to the light in the headlight shell that was for the warning light as a defacto oil pressure warning light that will only tell me no pressure at startup but will be a better indicator of voltage being present. Jury is still out on that.
On the Murphy switch gauge suggested by motorson I wonder if the seller knows the pressure the switch closes at? I don't see it in the listing and my guess is much higher OP than my Brit can generate. I'll ask but would not be surprised if they did not know.
On a side note, I finally decided to go with Pazon ignition in 12V positive ground so that decision is made. I figure what the hell. Don't need to reinvent everything and the electrons won't care. Plus a bit of originality is good once in a while so why not positive earth.

You might consider the cheap auto/MC relays at the junkyard; they have proper locking connectors and the right steel/plastic weather proof cases compared to the plastic parts store pigtail ones; clip off the wires a good distance on the harness side to get the locking connector and to be able to stagger/hide and other wise make tidy your wires' crimp joints.

I can see that I sort of went off on a tangent compared to where you were headed with your oil pressure switch idea. The Murphy switch gauge has an adjustable contact point and the gauge needle is the other contact. So, they are not kidding, the gauge IS the switch. Kind of cool but no liquid filled gauges or anything like that.

I'll be looking forward to seeing your finished schematic.

Cheers, Dan.

xbacksideslider said:

You might consider the cheap auto/MC relays at the junkyard;

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That would be a great way to go but I live on an Island with no junkyard and the cars that get to the end of their lifespan are big business for transport off the island to scrap yards.
Maybe I can get lucky and harvest something before they get loaded but bgenerally it is frowned upon by the transporter.
Not like the old days

xbskt said:

If the relay has a NC contact I may run it to the light in the headlight shell that was for the warning light as a defacto oil pressure warning light that will only tell me no pressure at startup but will be a better indicator of voltage being present. .

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Most relays are double pole, double throw....that is, two sets of contacts, each with a NC and a NO. You could run the warning light off the NC contact of the "A" set in the above schematic. That way, if the oil press. Sw. fails to come up to pressure, the light will tell you.

A good source for electronic components is DigiKey. Google for website. you do not need commercial account and there is no minimum....also they have good selection of parts. You can probably find a relay with matching socket and hold down spring.

Slick