12 volt source

[Scotty56 Lurker Find all posts View Profile Close Scotty56]

Can any one tell me where I can find a 12 volt source under the bonnet of my Prado 120 TD which is live with the engine running but killed when the engine stalls(stops) but ignition is still on I need it for a safety cut out switch. I have checked all the fuses but they all stay live when the engine stalls.

regards

Kim

[speedcomm Senior Member Find all posts View Profile Close speedcomm]

Re: 12 volt source

I doubt you will find such a supply Kim, my thoughts would be to find the oil pressure sensor and see if you can use that as a drive for a relay running off the battery or ignition, this would then only give you power while the engine has oil pressure, this a trick I have seen being used to join batteries in a dual battery setup, using a basic solenoid so batteries are joined while motor is running.

[Guest Close Guest]

Re: 12 volt source

Redarc make a device for this. http://www.redarc.com.au And I think someone was giving one away in the for sale area a few weeks ago?

[Jacques Lurker Find all posts View Profile Close Jacques]

Re: 12 volt source

Just curious Scotty, why would you want a safety cut out switch in a diesel?

[jeff s Avid PP Poster! Find all posts View Profile Close jeff s]

Re: 12 volt source

Ditto Scotty, Why for you need this?????

And I think the oil pressure one is the best. But if its like the one on my bike it is a little tricky.
As in, the oil light is part of the cuircuit. power goes from battery, to oil light to oil pressure switch with the one wire.
So when no oil pressure the cuircuit is made because the pressure switch is closed and connected to earth through the oil pressure thread.
When oil pressure is there, the contact is broken, causing the light to go out.

But as I said, that was my bike. and the pressure switch had only one wire.... I really dont know what the Prado one has.?.?.?


Very interesting tho.. will watch this and see where this leads us....


Jeff.

[Jacques Lurker Find all posts View Profile Close Jacques]

Re: 12 volt source

The alternator sensor wire (i think it is yellow & white but stand to be corrected) may also do the trick - either that or the oil pressure sensor.

[jl4049 Lurker Find all posts View Profile Close jl4049]

Re: 12 volt source

You can use the oil pressure switch if you use a relay with normally closed contacts, wire the contactor side of the relay, positive from an ignition controlled feed, then earth through the oil pressure switch, wired this way the relay will cut power when the oil pressure switch is made i.e the engine is stopped and will allow power through once oil pressure is acheived. Only thing is it will take a couple of seconds to cut the power if you stall as the oil pressure won't drop to zero immediately and it will take a few seconds of cranking to build enough oil pressure to open the switch when starting.

[jeff s Avid PP Poster! Find all posts View Profile Close jeff s]

Re: 12 volt source

You can use the oil pressure switch if you use a relay with normally closed contacts, wire the contactor side of the relay, positive from an ignition controlled feed, then earth through the oil pressure switch, wired this way the relay will cut power when the oil pressure switch is made i.e the engine is stopped and will allow power through once oil pressure is acheived. Only thing is it will take a couple of seconds to cut the power if you stall as the oil pressure won't drop to zero immediately and it will take a few seconds of cranking to build enough oil pressure to open the switch when starting.

Thats sounds right I think? Power from an ignition on only source to the positive terminal on the coil of the relay, then the earth on the coil to the oil pressure switch (OPS).
Then a power wire (also only on while ignition on) to the normally closed contact and through to your items you want powered only while OPS is open circuit. (oil pressure)

Yeah, then while ignition was on, engine stopped, oil light on, relay coil would be hot because of earth through OPS. The power through NC contact would be open, Items isolated.
Once engine running, OPS would open circuit, dropping power through relay coil, closing NC contacts, sending power thorugh realy to items you want powered only when engine is running.
If engine stalls, ignition still on, OPS would close, light would come on and relay coil energised, opening NC contacts, dropping power to said items.

Is that right?

[Scotty56 Lurker Find all posts View Profile Close Scotty56]

Re: 12 volt source

Thankyou all for your responses,

sorry I haven't replied sooner but I have been away for the last couple of weeks enjoying the Murray River. The reason is to enable a safety cut out for a LPG fumigation system which I will be doing some testing as part of R & D for an importer, so if the engine stops for any reason the LPG will be cut-off even if the ignition is still on. On a petrol engine this simple as you can use the fuel pump circuit or coil negative but on the Prado 1KZ-TE engine not so simple. I have looked at the oil pressure switch but I think it is part of a CAN Bus system as there are 2 wires neither of them having 12volts both appeared to have 5 volts and the oil light remains on even with the connector disconnected off the switch (yes it was the oil pressure switch). The alternator was my other option but I was unsure if it had a wire which was only live when the alternator was charging similar to the old Ford Falcon's and Holden Gemini's which used them for auto chokes and fuel pump relays. I will look for a yellow/white wire but I will have to strip back some of the loom to see it as there is very little room at the back of the alternator.

thanks again

Scotty

[photoprado Avid PP Poster! Find all posts View Profile Close photoprado]

Re: 12 volt source

If the oil switch is can-bus, then you could perhaps put a T in the connection and add an old style switch?

Michael

[MickL Addicted PP Member Find all posts View Profile Close MickL]

Re: 12 volt source

I have looked at the oil pressure switch but I think it is part of a CAN Bus system as there are 2 wires neither of them having 12volts both appeared to have 5 volts and the oil light remains on even with the connector disconnected off the switch (yes it was the oil pressure switch).

I'd double check that... sounds like the oil level switch.

The oil pressue switch is a single wire, Gray connector.

Mick

[Scotty56 Lurker Find all posts View Profile Close Scotty56]

Re: 12 volt source

Thanks Mick and Michael

Oil level switch mmmmmmmmmmmmmm well I didn't know they had one so maybe I have been disconnecting the wrong switch ops: ....Mick where exactly is the oil pressure switch as the connection I have been disconnecting is below the oil filter.
Michael I have thought of the 'T' fitting but I would prefer not to if I can but if all else fails I will do that.

Scotty

[MickL Addicted PP Member Find all posts View Profile Close MickL]

Re: 12 volt source

I didn't know they had one

A lot of diesels (all :?: ) do.
In the wiring diagam it's listed as a Gray, 2 wire connector.

The oil pressure switch is also listed as a gray connector but single wire.

the connection I have been disconnecting is below the oil filter

How far below? The oil pressure switch is right next to the filter. It's hidden by the filter its self. To the bottom right of it.


Mick

[MickL Addicted PP Member Find all posts View Profile Close MickL]

Re: 12 volt source

This should help you out:




Mick

[Scotty56 Lurker Find all posts View Profile Close Scotty56]

Re: 12 volt source

Fantastic Mick

thankyou I nearly took the oil filter off today to have a look but didn't get around to it as we had to pick our van up from Jayco
(after 3 months leaving it with them to do a couple of warranty items :? )
Hopefully I will get a chance to have look and also play with the air con this weekend.

thanks again for all your help

Kim