SA oil pressure and pressure sensor question
 

Heya chums!

Several warning lights on my instrument cluster don't 'bulb check' when the key is turned on. All bulbs are good. This lead me down a path which resulted in a nice Electromotive dual oil pressure/temperature gauge landing on my doorstep. In considering its sensor locations, The original factory oil pressure sensor next to the oil filter seemed like a logical conclusion. However, it raised a question: What the heck is that sensor's purpose? It doesn't even exist in the wiring diagrams that I have. There is a low oil level warning light (which doesn't bulb check despite having a good bulb), but there is no LOW OIL PRESSURE idiot light anywhere I can see, and of course, no factory gauge. Further confounding matters is when a test light is applied to the sensor pin, there is continuity both when the engine is off and when started and revved. The light doesn't dim or become brighter (yes, a multi-meter would be better), it just remains constantly on. Of course it's ancient and could simply have failed, but can anyone enlighten me as to why this sensor is present?

Next, Racing Beat says "Oil temperature entering the engine should never be allowed to exceed 205°F"
That leads me to think that an oil temperature sensor should be installed between the oil cooler output and the engine. My thinking here is that when i'm lapping a road course, the oil coming out of the engine is going to be damn hot for obvious reasons. Probably not hotter than the oil can handle, but possibly hotter than 205. Therefore, considering RB's statement, I should be interested in how good a job the oil cooler is doing by measuring its discharge temp rather than worrying about the engine's discharge temp. After all, if the engine is having catastrophic problems, I would probably be able to identify them just as clearly by sound and coolant temperature as with oil temperature.
Thoughts?

Thanks in advance!
b

The light issue could be a bad ground.

The low oil indicator sensor is in the oil pan. I can't speak for the Canada 1979 SA version, but the U.S. spec did not come with an oil pressure gauge.

I installed a pedestal block to mount the oil pressure/temp gauges in my 1979. I mounted a water temp gauge in the back of the water pump house. I converted my old cast iron water pump housing to an S4 aluminum one.

Another good place for the water temp sensor in the 1979 is the top of the water neck. There is a nice flat spot on top. The only issue with this spot is that it is on the radiator side before the thermostat.

https://www.rx7club.com/1st-generati...-12-a-1116674/

There is a a relay on the drivers side fender relay mounting area (several there) that makes the all console warning lights light up at key on.Its called the choke and check valve. Is its bad you may see an issue like the lights not working. As stated also check your grounds.

I've use the oil filter sandwich adapters on two or three vehicles now for oil pressure and oil temp readings, always worked well for me. The eBay ones work fine so long as you get the right adapters with the correct threads for your filter.

That 205 degree oil temp is very conservative, I'm quite surprised they'd recommend that. The RX-8 I built has oil temp and oil pressure gauges on the filter sandwich adapter. Oil temps, when warmed up and moving, are almost always between 170 and 180 degrees F. When stopped for a while or parked, the oil temps can get up to 210 degrees. I'd be surprised if a first gen's temps would be that low because they only have one cooler mounted directly under the radiator (or a beehive oil heater with coolant) which isn't as good of a system as the RX-8's dual front mount oil coolers in front of the radiator, right behind the bumper cover.

SAs don't have oil pressure switches or senders, it's not in the wiring diagram because RX-7s didn't get senders until 1981.

'78-80, all you had was a low oil level idiot light.

I have never seen oil temps over 180F, measured in the pan, on a front mount oil cooler setup.

RX-8s run the oil hotter because their coolers are not located very well, and Mazda wuns the oil HOT. I think they still have the thermopellet that cuts oil flow to the inside of the rotors until they get super hot, too.