What is the purpose of the FC thermoswitch?
 

If FCs don't have electric fans, what is the thermswitch for?

Do they only come on cars with automatic transmissions?

FC's have fans in front of rad. The thermoswitch has a different activation temp for N/A and Turbo.

Depends on which switch your talking about also. The main thermoswitch that is behing the waterpump tells the ECU what the temp of the coolant is to accommodate the proper fuel mixture.

Now SOME 7s (IIRC mainly autos w/ac) had another switch that went into the thermostat neck that activated a pusher fan that was mounted on the a/c condenser to help with the a/c efficiency

No they don't. They have fans in front of the AC condenser.

The car wouldn't even necessarily need an engine coolant thermoswitch for that fan.... just ON/OFF with the AC.

The thermoswitch that FD owners use to lower their fan temperature.

The switch controls the condenser fan, its on at 207f and off at 194f according to the factory service manual.

I'd assume they did this as somewhat an "any helps better than nothing" when it starts getting hotter than intended.

Semantics. The fan is still in front of the rad

I guess the following answers the second part of your statement.

Thermoswitch on the back of the rad near the bottom tells the ECU when the coolant is up to temp, 90% of the time this switch is closed, its only purpose is to richen the mixture during warm up.

Yeah, and the intercooler is technically above the brake rotors, but that isn't a helpful description...

Is that on autos only?

its an S4 thing. S5 doesn't have it

My 1986 S4 coupe has this switch. The tab broke off so I'm searching for a new one. Anyone know where I can get it? From what I could find, the factory part # is 18-840C maybe?

Also, my car is a manual with A/C... I believe it's the Canadian Luxury model?? I'm not sure what accessories this was supposed to have. But does this switch only come on automatics?
Would that mean that my car's either had an engine swap or a manual conversion? It appears to be stock.

That is not the part number. Mazda groups their part numbers differently. When I get to work I'll look it up and see if I can post it for you. It may still be available. You'd be surprised at what is still available for these cars.

its possible the water pump or thermostat housing got swapped too, not just the engine. all the wiring harnii should have the connector for the fan switch, it just wont have the fan, or the switch.

the switch is either E301-18-840A or F8B5-18-840

Finally, a usable part number :crackup: thank you!

So theoretically, my car could have a fan in front of the A/C condenser? Or would it be behind it?

And if it doesn't have a fan then this switch is just... Irrelevant? Having or removing the switch would have no effect what so ever on the car?

Saw that switch new on either Atkins Rotary site or Ebay just a few days ago.

You can get the fan switch on RockAuto as well. Keep in mind that S4 switches turn OFF at the prescribed temperature. S5/FDs turn ON. I'm running a 1974 Subaru GL fan switch on my 20B's Taurus fan. $8 from RockAuto, stock M16 threads, On@204, and uses a regular bullet connector. Win!

I'm wiring up my car to a Haltech standalone. As of right now would like to continue using the factory S4 clutch fan setup. Am I going to need to adapt the thermoswitch sensor to my new ECU? I'm retaining my A/C which will be primed through the standalone. Not sure if it's all connected to the same system. The green thermoswitch sensor at the back of the water pump - is this for the stock ECU fuel enrichment or is it for the A/C as well? I'm doing my reading but still a bit confused.