Looking for engine running signal

Post by **Merlin** » Tue Jun 23, 2015 2:26 pm

I get you. Would you put your 12V feed on the live side of the bulb or does it not matter?

I might test this tonight. I will be at my 4G tonight and can easily get to the oil pressure switch wiring.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Tue Jun 23, 2015 2:32 pm

This is where you want to take a feed off the circuit, right?

Go after the bulb (so the same as where everything else is also connected).

Post by **Merlin** » Tue Jun 23, 2015 3:17 pm

OK next question, what happens if the oil pressure drops and the oil pressure switch earths off the circuit, will that have any effect on the 12V feed after the bulb?

I need to go and play with my test lamp

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Tue Jun 23, 2015 3:36 pm

Yes, after the bulb, the circuit will drop to zero.

Post by **Merlin** » Tue Jun 23, 2015 3:37 pm

That wouldn't be good for the OP's application? It would be fine before the bulb though?

Or you could just disconnect the oil pressure switch, it is not of much use anyway.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Tue Jun 23, 2015 4:03 pm

I thought that was exactly what he wants?

When the engine is running he has 12v.
When the engine is not running he has 0v.

Post by **Merlin** » Tue Jun 23, 2015 4:36 pm

What I meant was what if oil pressure drops while the engine is on and the oil pressure switch does what it is meant to do and turns on the oil pressure warning light.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Tue Jun 23, 2015 4:57 pm

Yes, then you'll lose the signal.
But you should be shutting the engine down then anyway

Post by **Merlin** » Tue Jun 23, 2015 5:02 pm

He is wanting to link his alarm/immobiliser up to it

An unlikely scenario I know.

Would be loose the 12V if it was wired on the other side of the bulb? It means getting into the dash.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Tue Jun 23, 2015 5:30 pm

Well, what we've come up with fits the original spec;

alinton wrote:it wants a 12v signal that's there when the engine is running, i.e. not when ign is on solely.