regarding FC thermoswitch / thermosensor
 

I orderded one from Ray at Malloy703-490-8170 (talked to Brian actually but he also knows abut the club).. PN41-18-840 same as Dale's 3rdgen archive thread here: https://www.rx7club.com/showthread.p...6&page=1&pp=15

BUT

mine isn't stamped "95", instead it says "97M"

maybe the 95 and 97 don't correspond to switching temperature?? just a thought..

btw i also ordered a radiator cap and ast cap each $14.25. the fc sensor cost $47 and $5.00 shipping for all 3 pieces, shipped 2 day!
:icon_tup:

so has anyone else noticed the stamping on the thermoswitch? i would test when the fans come on but i haven't installed a aftermarket temp gauge yet.

Just looked at the pic in my thread on the thermoswitch - it IS marked 97. I think we're just rounding down to 95 :).

It's worlds better than the stocker, regardless!

Go get you a temp gauge soon!

Dale

FYI, from my research and testing, the thermoswitch only shifts the fans' operation from LOW>>MED or MED>>HI. The thermoswitch alone will NOT turn the fans on.

more info here (especially my last post in the thread): https://www.rx7club.com/3rd-generation-specific-1993-2002-16/2-trigger-cooling-fans-462760/


-s-

read through your thread scotty..

what does cause the fans to switch on then in the case of the thermoswitch? are you saying that with the fc switch installed all it will do is make the fans run at a faster speed than with a fd switch.. but not affect the temperature at which it switches on/off at all?

where is the thermoswitch on the diagram? is it one of the relays..

i don't know much about electrical systems but im trying to learn lol

The thermoswitch does turn the fans on also. Since I made the change to the Miata TS (basically the same as the FC TS, but with a different connector), the fans come on sooner and much more often.

From my understanding (because I'm reworking the electrical side of my coolant system at this time), it that the thermoswitch pulls in relay #3. I know that's correct.

According to the FSM, the stock thermoswitch closes it's circuit and pulls in relay #3 at 226F (108C).

The thermosensor pulls in relays #2 & #4 at 221F - 226F. So on a stock system, the thermosensor would turn on the fans before the thermoswitch could. Thermoswitch would kick it from LOW to MED, or MED to HI only (depending on A/C on or off). Again, that's on the original thermoswitch.

However, with the FC thermoswitch, and the fact that it closes the circuit at a lower temp than the FD thermoswitch, I'm guessing the FC thermoswitch would activate relay #3 before the thermosensor would acitvate relays #2 & #4.

- JyRO

I tested the miata switch. One problem was that the off temp was only a few degrees below the on point. This would cause frequent cycling for short periods. The FC switch may have a lower off point (delta), and work better.

oem: with ac off, fans hit low at 221F and med at 226F.
with FC switch: with ac off, fans hit med at 207F, and will only see low speed if ac is on and fans were not already on.
(For a few odd models, FC switch will still need relays 2&4 tripped, so fans will come on at med speed at 221F.)

In all cases, needle could be burried in red and unless AC is on, fans will not go to high.

Here's a link to the cooling system electronics diagram, from the page I referenced earlier. It's huge so I'm not going to insert the photo in this thread.

https://www.rx7club.com/attachment.p...hmentid=131481

The thermoswitch is located to the right of the fans on the diagram, labeled WATER THERMOSWITCH (FAN). Follow the line with dark purple dots, and you can see that the thermoswitch connects to Relay #3. The thermoswitch is what activates relay #3, which will cause the fans to increase their speed. Relay 3 will not activate the fans by itself, I've tested this.


However, after looking at the diagram again, I noticed that the thermoswitch is also connected to the Coolant Fan Control module, so it's possible that the Coolant Fan Control Module is activating the fans when the Thermoswitch is activated. This will only work for cars with the Cooling system recall, and fits with KevinK2's experience.






By the way, I've been planning to design and build a replacement for our stock cooling system electronics. I haven't gotten around to it yet, but if there were 5+ people interested then I could have it ready before summer. It would include a digital temp gauge and the user could control the fan's turn-on and turn-off points. The FC thermoswitch would not be needed. PM me if you want more info.


-s-

My fans don't come on and off for very short periods. There is a pretty reasonable cycle in between, even if I am idling after a long period of driving in hot weather. IIRC, the cycle is ~1-2 minutes on, then ~2-3 minutes off if the car is sitting still. Don't put money on the accuracy of those times - they're just from memory, since I've never timed the cycle.

perfect i think this was the missing piece.

I also have the Miata TS with a basically stock car. While I've never timed them either, those cycles and times are close to to what I get, maybe even slightly longer off.

Since the fans will turn off at a certain temperature, it's possible that KevinK2's cooling system dissipates heat faster than the people with longer cycling times. This could be due to a number of things, especially the water/coolant ratio in your system.

-s-

oem spec is on at 226F, off 214F, delta =12F

miata test ... on 206F, off 200F, delta =6F

typical euro switch delta is about 10F

FC =?

The miata switch is fine .... higher delta would reduce fan use a bit.

I have oem, and use parking lights to get fans on at low at about 210F. With fully sealed ducting and mazda comp rad, they rarely come on, even in summer. Not my daily drive.