Too many sensors!
 

'81 SC. The factory 3.0L engine has what appears to be four temperature sensors and two pressure sensors on it.

Right chain case lid temperature switch: 930 606 117 00
Left chain case lid temperature switch: 911 617 117 00
Oil breather cover temperature switch: 930 606 117 01
Front of engine remote temperature sensor: 901 641 632 00

Front of engine oil pressure transmitter: 911 606 111 03
Top of engine oil pressure switch: 911 606 230 00

I'm operating under the assumption that all four of the switches tie in to the same oil light on the druck/temp gauge. Is this correct? If not, what are they used for?

That leaves a single oil pressure sensor and one for temp. Why are these at the front of the engine? Is there a difference in pressure between the front of the engine and the breather tube lid? What about temperature?

Right chain case lid temperature switch: 930 606 117 00 - dunno, only SC has this. Probably CIS warmup-related...
Left chain case lid temperature switch: 911 617 117 00 - thermo-time switch (TTS) - grounds the Cold Start Valve (CSV) for extra enrichment while cranking for cold starts below a set temperature
Oil breather cover temperature switch: 930 606 117 01 - dunno , my turbo had something different there. :D probably related to CIS warmup in some way.
Front of engine remote temperature sensor: 901 641 632 00 - I believe this one drives the gauge, but would have to check wiring diagram
Front of engine oil pressure transmitter: 911 606 111 03 - pressure sensor, drives the gauge in the dash
Top of engine oil pressure switch: 911 606 230 00 - "idiot light" sensor, drives the warning light in the gauge

At least one of your temperature "switches" is actually a sensor that drives the temperature gauge. Would need to look at the diagram be sure which one.

Pretty sure the other temperature switches do "stuff" to CIS - most likely to alter the way it behaves during warmup.

My guess would be because these readings are more indicative of the temp/pressure of the oil in the engine - tapped into an oil gallery that feeds the top-end, IIRC.

One is a pressure sensor (for the gauge), the other is a pressure switch (for the idiot light).

The temperature sensor drives the gauge, The TTS drives the CSV for cold starts; I suspect the other temperature switches control CIS warmup in some way (but my 930, which originally had CIS as well, never had these - so sorry, dunno :D )

TJ,

Find a good reference manual for your car and learn the basic instrumentation. A Bentley SC Manual although has some typos is still an excellent reference manual. To answer your question, only one of the switches you mentioned controls the idiot light on the dashboard. The other thermal switches operate at different temperatures namely @ 15°C, 35°C, and 45°C. The individual temperature switches are marked accordingly on the switches. Bentley has good pictures and description how they work.

Tony

You got a 911 US model with lambda/ECU controlled CIS.

- the temp switch on the right chain housing is a 15 °C switch, which opens beyond 15 °C and lets the ECU switch form Open Loop (no lambda regulation but fixed value far static enrichment while col running

- the tempmswitch on the oil breather cover on top of thge engine is a 35 °C switch, which closes beyond 35 °C – it tells the ECU that beklow 35 °C it should extra enrichen when accellerating from idle.

All mentioned here:
https://nineelevenheaven-wordpress-com.translate.goog/der-911-us-sc-3-0-motor-mit-g-kat/?_x_tr_sl=de&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wap p
(Google translated till I translate to english – or someone else :-) )

For your Carb conversion, You only keep the oil pressure switch by the breather and the oil temp and pressure senders up front.
All the others are Lambda system related and are not needed.

I was hoping to remove ALL the factory sensors and switches, and utilize my Speedhut gauge and senders. One oil pressure, one oil temp. Programmable warning light based on readings. The dream was to put them both back by the breather. It'd likely work for the pressure, but I'm not so sure about the temp gauge - It wouldn't be submerged in oil, just kinda hanging out and occasionally getting splashed.

Early cars had the oil pressure sender back at the breather rather than off the oil feed for the Cam towers.

http://forums.pelicanparts.com/uploa...1648409416.jpg


There are some early senders that have both the pressure sender and switch in one. The 993 also had a combined function sending unit as well. I do not know what the speedhut sender looks like but you might be able to mount it in the rear like early cars. You would need to change your oil feed line to the cam tower as well..

john

That's the hole I intend to use for the pressure sensor. Unfortunately, the temp sensor is a different sender, so I need to use another hole for it. It's too long and the connector juts out too much to reuse the factory temp sender location. I was hopeful that one of these other switches would be a good place for an oil temp sensor, but it doesn't look like any of them are actually submerged in oil - They're just reading ambient temp. Back by the breather cap would be the perfect place. Shame.

My gauge can't be configured for any old sensor, either - I have to use the ones they send with it, otherwise I'd get myself a 2-in-one temp/pressure.