alternator indicator light via blue wire?

[GH85Carrera]

It is a custom job. I had one of the "Speedometer" shops do it. I think I had Palo Alto speedometer do it. It has been a long time. They did a great job, and I just love how it looks like what the factory should have done. It looks right, and works right.

It takes a 4 to 6 weeks so it was a winter time modification. Pull it out, send it in with what you want, and send money!

[Geneman]

thanks walt very much for that description . now it makes sense. same voltage arriving at bulb cancels out!! i am electron flow challenged...

speaking of which. my big BIG patrick motorsports red idiot light fixture in the clock hole. does no light upon pwer turn on. the wire is hot to the sensor because when you ground the wire, the bulb lights.

i had to put a brass reducer/adaptor to get the sensor to mount on the engine. so is the fact that it is brass the reason why will not light? must i jump the sensor grnd to the motor?

btw . just found out one of the BRAND NEW MSD6AL boxes i ordered was bad right out of the box... unbelieavable..

[Geneman]

indeed , really love that voltmeter modification glen! thanks

[Walt Fricke]

The idiot light switch is a normally closed single pole switch. With no (or very low) oil pressure, the switch is closed, connecting the wire connector to the case ground. So if the warning light's bulb has +12VDC supplied to it, the idiot light switch connects to ground until the oil pressure opens the switch. Sounds like you have the light wired properly.

Me, I like to use an Autometer switch, which takes a lot more pressure to open - the stock one doesn't close until pressure drops to about 0.4 bar. Autometer typically has NPT threads, so you need an adapter to the metric, but no problem.

Brass conducts just fine. I suppose it is possible that use of Teflon tape on the threaded joints might interrupt this, though I doubt it. To test, get power to the light, and then ground the body of the sensor case.

My guess is nothing will happen because the sensor is shot and not making contact inside. The sensors aren't expensive. A PITA to replace in the car, though. I favor using the VDO combined oil pressure and idiot light unit - two connectors on top, not just one. You use that where the oil pressure sensor goes, which has great access. You just have to run a bit of wire back to it for the idiot part.

The idiot sensors don't care what voltages get transmitted. The oil pressure gauge has to be matched to the OP sensor. Early on the gauges were 10 bar or 150 psi. At some point - the SCs? - Porsche switched to a 5 bar/75 psi sensor and gauge. You don't want to run a mis matched combination.