12 replies to this topic

[mini-luke]

I need to find a switched live that's live when the ignition is on, but isn't cut off when the key is turned to start, is there such a thing on a Mini?

Thanks

[mini_in_progress]

is it a trick question? lol if its powered to ignition live it will be on when the ignition is on and when ignition is on and engine running becasuse after you start the car the key goes back to ignition.....

[mini-luke]

is it a trick question? lol if its powered to ignition live it will be on when the ignition is on and when ignition is on and engine running becasuse after you start the car the key goes back to ignition.....

Nope, the switched live briefly goes off when the starter motor is activated. That's a problem, as the switched live is used to power a relay that cuts the power to the starter motor, which if it was fed permanent live would slowly drain the battery.

[lrostoke]

The white wires are switched live and should stay live when the starter is spinning,

They must stay live because it is also the feed to the coil (on a ballast ignition car the resitive wire takes a feed off the white wire)

[mini_in_progress]

is it a trick question? lol if its powered to ignition live it will be on when the ignition is on and when ignition is on and engine running becasuse after you start the car the key goes back to ignition.....

Nope, the switched live briefly goes off when the starter motor is activated. That's a problem, as the switched live is used to power a relay that cuts the power to the starter motor, which if it was fed permanent live would slowly drain the battery.

i dont get it.. lol what you trying to do? all cars do that you never noticed why your dash lights and radio cuts off when starting?

The white wires are switched live and should stay live when the starter is spinning,

They must stay live because it is also the feed to the coil (on a ballast ignition car the resitive wire takes a feed off the white wire)

good point i think for a second tho it does go off but soon as the swich on ignition reaches full turn its connected again..??

Edited by mini_in_progress, 29 February 2012 - 09:27 PM.

[lrostoke]

turn the key quiicker then ha ha, If it does actually switch off for a fraction I doubt theres anyway round it without a different type of key.

[Dan]

The ignition circuits are live throughout cranking, the accessory circuits aren't I believe. The appearance that power is cut to the ignition curcuits comes from the volt drop caused by the starter. Are you fitting an active immobliser?

[mini-luke]

The white wires are switched live and should stay live when the starter is spinning,

They must stay live because it is also the feed to the coil (on a ballast ignition car the resitive wire takes a feed off the white wire)

Perfect, thanks, hadn't thought of that.

[mini-luke]

The ignition circuits are live throughout cranking, the accessory circuits aren't I believe. The appearance that power is cut to the ignition curcuits comes from the volt drop caused by the starter. Are you fitting an active immobliser?

Yes, someone has disabled my standard one and the keys are missing.

[dklawson]

As above, white wires are hot whenever the key is in the run or start position. The voltage dips when the starter is turning but the white wire voltage is not switched off.

If you need to hold the power "up" during cranking there are some workarounds. Consider fitting a large electrolytic capacitor the the supply line to the device you are powering and place a power diode in the line feeding the capacitor. The capacitor will charge to full voltage when you first turn the key. When the starter is cranking you will still have the voltage drop in the car but the diode will prevent the backflow of current out of the capacitor into the car's electrical system. Anything downstream from the capacitor will remain powered at 12V at least for a while (depending on the current drain of the device) until you stop using the starter motor. Once the starter motor stops, full system voltage will again pass through to the device.

[mini-luke]

I should be OK with regards to voltage drop, it's only a relay and when it is drawing power it should also be preventing the engine from turning over, so no voltage drop. I made the mistake of wiring it to an accessory wire that doesn't receive any power when the engine is turning over, so the relay would close allowing the engine to start.

Thanks all, was loosing the will to live with this wiring!

[mini-luke]

Sorted - hooked up to the white wire and is working perfectly. The voltage drop is pretty hefty with the starter motor turning, 9v, but not enough to worry the relay.

[Dan]

Yup, that's why ballasted ignition was invented.