So I've been having overheating issues and have concluded that my fans no longer turn on when needed. I just bought this car about 6 months ago and have been filtering through issues here and there. Overall the car is in great condition. Completely stock 91 dx hatch. Still obd0 with the d15b7 non vtec. I've been researching and the fan switch is supposed to be the 2 wire sensor on the back of the block beside the oil filter for obd0 engines. But I've also read that the sensor on the thermostat housing is also the fan switch but for obd1 engines. I have the sensor on the back of the block but I also have the sensor on the thermostat housing but it does not have a connector nor can I find the connector or wiring in the engine bay anywhere. My question is which sensor is the actual fan switch? I was told the engine had been replaced at some point but with a different d15b7, so it should all be the same. If that sensor on the housing is supposed to be connected, where does the wiring go? From what I've read there should be a yellow/green wire and a ground wire but I found those at the sensor on the back of the block. Please help thanks

2 wire sensor on back of block with yellow/green and black wires

Sensor on thermostat housing with no connector or wiring to it
I have read that you can extend the wires over to the thermostat housing and wire it in? I already have the connector for the thermostat housing so I can wire it in. Is it as simple as that?

 

The switch on the back of the block is the one for the cooling fan on the 91.

 

So I actually just replaced that sensor and it fixed my fan issue. Any idea why I have both sensor locations? From my understanding my engine is obd0 and uses the 2 prong sensor on the back of the block and obd1 uses the thermostat housing sensor. Is it possible to use an obd1 block and not use that sensor at all?