I'm planning on doing the miata-thermoswitch mod. but i'm not sure where the thermoswitch is. the only things i heard is, that it's "behind the thermostat-housing".
i got a service manual, it sais i gotta take out the ic, intake elbow, waterpump, alternator etc. now, what is right, what is wrong? Could someone clearify that?

Chris

 

I just replaced my water pump housing, so I replaced my thermoswitch at that time. Here's the poop: The switch IS behind the filler neck body. If you pull the crossover pipe and it's mouniting bracket, you will see a plug going into the filler neck housing body with a green body to the connector. This is the water temp thermoSENSOR, which tells the ECU what temp the engine is (NOT the temp gauge sensor). Directly underneath the thermosensor and slightly towards the driver's side of the backside of the filler neck housing body, you will see a plug in the housing body with a black connector. This is the thermoswitch. Jesus! How am I going to get at that?

So near as I can tell, if you want to replace this without pulling the water pump housing (which is what the manual is describing, that's why all the parts removal), you need to 1) drain the coolant; 2) CAREfully remove the thermosensor (the body will have weakened by now and may self destruct upon removal); 3) remove the thermoswitch and replace it with the new one (make sure there is a new rubber O-ring, there should be, but never hurts to be sure); 4) splice the Miata connector to the wiring harness, replacing the black connector; 5) place the thermosensor back in, you can re-use the aluminum washer; 6) generally curse Mazda for creating such a bearish engine to a) work on, and b) get the air bubbles out of; and 7) enjoy the lower fan turn on temps.

Does this help?

 

I ended up removing the alt. That made it much easier to get to. I didnt drain the coolant however, instead I just took out as much as I could from the filler neck and my AST. I did have a little coolant leak out though when I pulled out the thermosensor and the switch. Then I cut off the connector for the thermoswitch and replaced it with one I pulled from a protege at my local junkyard, since they use the same switch as the miata. Then I put everything back in and I was rocking.

Here is some advice. Be careful when pulling off the connector to the thermosensor. I cracked mine. *doh* and ended up having to go back to the junkyard to find that connector and replacing that one too.

 

ok, thanks to spurvo and goobers, very nice and detailed now i know the facts