Hello again, I was in the process of putting the Thermostat housing cover on my turbo S4 engine, and I noticed what appeared to be a sensor was bent protruding from the Thermostat housing. Picture No.1

I removed this part to find the end was covered in what looks to be Antifreeze. Picture No.2 I tried my best to clean this part by soaking it in Purple Power and scrubbing it with a brush. What looks to be some type of seal, o-ring broke off in this process. Here it is know. Picture No.3

I can not find the name of this sensor/part in my Haynes manual. In Illustration 10.2 i found part No. 11 that connects to this sensor/part. This part No.11 is called a "Water thermo switch connector( Models with automatic transmissions)" Picture No.4 I have a manual transmission tho.

What is the name of this part? should I buy a new one? I think I should. The closest part I could find on Atkins.com was under the Coolant Sensor 79-92 section. I really wan't this engine to stay cool when operating, so this little part is important to me. Thank you.




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You don't NEED it (obviously since it doesn't look like anything was hooked up to it) it was mainly used on the auto cars for an electric fan in front of the a/c condenser. But its the perfect spot for the probe for an aftermarket temp gauge, which is highly recommended because the stock ones are not very accurate

 

This is indeed the fan switch for the A/C aux fan. As a backup to the main clutch fan, it is triggered to come on at 207 degrees (195 degrees for automatics). But what is odd is that the switch turns OFF at the set temperature.

Please do NOT use this location for an aftermarket coolant temperature gauge. In the whole system, this spot is AFTER the thermostat, meaning the gauge will read cold untill the thermostat opens. And should your thermostat decide to take a crap, you'll have no way of knowing it. A better idea is to drill & tap the water pump housing. My personal preference is to tap it for M12x1.5, same as the stock Coolant Temperature Sensor, and then use a brass adapter fitting to reduce it down to fit the more common 1/8" NPT or 1/4" NPT sensors. This gives you some flexibility in case you decide to use a stock sensor or go in a different direction such as with a GM sensor. LS2 Corvettes use the same M12x1.5 threads as our cars do, but you can get the sensor & connector anywhere for cheap.

Going back to the fan switch, the following is for if you decide to do an electric fan conversion.
The 89-92 RX7's fan switch triggers at 207, turning ON like with most other cars, but finding a matching connector has proven difficult in most cases. What I do is get a fan switch from a 1974 Subaru GL instead. Same threads (M16x1.5), nearly the same trigger temperature (ON at 203 instead of 207) and it uses a common bullet connector. Everyone wins