I just replaced the coolant temp sensor in my Manual 97 Mazda Lantis 323 1.8L DOHC 16 Valve BP , which had been malfunctioning and realized that something else seems to be responsible for reporting the engine temperature to the dashboard and turning the radiator fan on and off. I can't seem to figure out what it is though - and the previous owner told me that a mechanic he had taken it to had jerry rigged something so that the fan would stay on all the time - not sure why - but it doesn't seem to be coming on now. The dash display also sometimes reports the engine as being overheating when it's not actually hot. The temp continues to be reported even when the coolant temp sensor is disconnected.

I found this electrical diagram for the car, but I don't really know how to read it:

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  • I only see the one temp sensor listed top center of the diagram. Have you checked the relay for the fans? It should be located in the engine compartment somewhere. Oct 21, 2014 at 21:36

1 Answer 1


There are usually at least two. The one listed there is for the ECU (and possibly cooling fan(s)). There should be another diagram for the accessory/dashboard electronics, and that will tell you the wire colors to look out for for the other sensor. The engine mechanical section might give you a diagram of where the sensors are.

  • Yeah, on inspection I found that there is a second single wire heat sensor perpendicular and to the front of the ecu one which apparently controls the dashboard heat display. Oct 25, 2014 at 17:01

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