Hello,

The previous owner wired the fans in parallel (yay) to a toggle switch on the dash (what?) - I'm working to revert the cooling fans to act off of the thermoswitch.

The wires which normally plug into the cooling fan still get power when I jump the GRD and TFA pins in the diagnostics box, so it appears that all I must do is rewire the fans to plug into the normal place.

Is there any particular reason to run it off of a manual switch? Is there anything I should check before rewiring it as described and starting the car again?

I'm guessing I could check the thermoswitch (pot of water) and relay (bypass thermoswitch to ground) in isolation first.

Thanks.

 

I just picked up another Miata project and the fans are wired the same way. The PO said they "just stopped working" and then rewired them. Seems like a massive waste of time to have done this. I suspect the thermoswitch as well.

 

a) I checked the relay - it clicks when the thermo switch is bypassed

b) I pulled the thermo switch and tried to test it in a pot of boiling water - my mom held it with some tongs while I used a multimeter to test for continuity, and it was dead. It's supposed to close at 207 deg F, but it wasn't doing anything in boiling water.

I can get a new switch for $15 at RockAuto or $50+ from the Mazda dealer. What's the catch? Some say that the auto parts store variety don't close the circuit at a low enough temp, some say they work fine.

 

I've never had a problem with Rockauto.

 

+1 on Rockauto.

I suspect different dealers mark-up differently. If I need something OEM, I usually go to Rosenthal or Jim Ellis on the interweb. They're pretty reasonable. BTW, virtually EVERY part on your car is still available from Mazda. Another reason to love Miatas.

 

I ended up paying twice as much ($30) at a local Autozone because I'm impatient and wanted to be able to return it easily in case of a malfunctioning unit. Throw in a lifetime warranty and the fact it's not made in China and I'm pleased.

I wired the fans in parallel to the original cooling fan connector and wrapped up the whole deal in plastic sheathing. Now I have clean, solid, and protected wiring . . . for the fan. There are many more messes to sort out.

Fun fact: The PO ran one wire from the fans to the switch under the dash and another all the way to the battery. The only reason I can see to do that is that he didn't want to replace (or didn't know to replace) the thermo switch.