1999 NB 1.8iS electrics

  1. My model of MX-5 is: __1999 NB
  2. I’m based near: Sheffield
  3. I’m looking for technical help or recommendations on: __Electric fan

Hi all,

I have a question on the electrics on an 1998 / 99 NB 1.8iS. The electrics on this vehicle are quite confusing. The Haynes manual passenger compartment fusebox is nothing like what is actually there. I started looking as I was trying to find out if my electric fan (non-aircon model) was working. I’ve had no over-heating issues or movement of the temp gauge towards the red from normal, just curious. I’ve connected a battery to the terminals and know it works fine but cannot for the life of me work out how it is triggered. The little diagnostics box on the right hand side under the bonnet does not have a ‘test fan’ connector even though all circuit diagrams state it does. I understand that there is a sensor on the rear of the engine near the heater pipes that is supposed to trigger the fan but it has never been heard to run even when the engine has had a good run and immediately switched off. The passenger fuse box according the Haynes has a 30A big square fuse but my fusebox doesn’t and most of the actual fuses are in different places. It seems that the electrics of this model are different to all other NB’s. Does anybody know of a circuit diagram that is accurate for this model?

Cheers Stewart

This may help . .

USA Miata.net

Fuse Boxes

Fan Relay Position

As to the “test fan”, I read in an article that 1999 and 2000 model years do not have a TFA position!

I have read that the fan triggers at about 210 degrees (assume F as in a US article) and that people have never heard the fan come on unless they do a long run and then let it idle.

Here are the wiring diagrams I have for 1999 and 2000 which hopefully will help you

1999 Wiring Diagram
2000 Wiring Diagram

Awesome information, many thanks