Just Bought a Miata Thermoswitch!! Pics inside!
 

Autozone Wells TU146 $33

As you can see in the pics it has stamped numbers:

97deg 92deg 03k(?) 5189(?) Italy

I assume those are the temp ratings (206.6 F and 197.6 F), maybe k-ohms and serial#

One question, do I still need the fan mod after installing this or will the switch take care of my fans with no other mod?

I believe this will turn your fans on at about 99deg c, not sure on that though...

You won't need to mod your fans, unless you really feel you need to have a switch to play with. If that's the case, get a girlfriend instead :)

I suggest getting a small crimp connector and splicing it onto the end of the original thermoswitch wire. Bend it so it has good solid engagement - Ray gave me a little connector when I bought an OEM miata t/s and it wasn't very good.

Dave

Hey could you do an instal write up when you finish putting it in?

The miata switch will work just like the old switch, except the fans will come on about 10* sooner. If you want anything else, you will have to do a fan mod.

i dont understand this modification,,, why didnt mazda put a cooler thermo switch in themselves

Also use some sensor safe silicone to hold that connector in place.

Thats a good question. You would think that they should have done it. I can't think of any reason that they didn't do it.

Well, my fans have never come on after shut down but they will if I leave the ignition in the ON position. This is what I do everytime I get back home, I leave the car in the ON position until the fans come on and shut off (about 10mins). I thought this was due to the switch rating of 221 F is not reached until after the shutdown heat soak period.

I thought the Miata switch will activate them since it's a lower temp (207 instead of 221) ??? That's all I want...

There really isn't anything to it. You are just replacing the stock sensor with this one. The only tricky part is what you use to connect the new sensor. You can just use a spade connector (cut off the stock connector and solder on the space connector). The wires will most likely be brittle so you won't have to worry about cutting off the old connector, it will probably fall off. ;)

Running the fans when the car is off doesn't do a whole heck of a lot. The car isn't moving so no fresh car is coming across the radiator (that and the water pump isn't on either).

thats why you should get a turbo timer! and leave the fans on while the car is at idle for a couple minutes.

Hotter engines run more efficient, and Mazda originally intended the RX-7 cooling system to operate at a higher pressure (so it could run hotter without boiling over & overheating). But due to some problems with hoses cracking/bursting from the pressure (supposedly caused by people not allowing the car to cool down before shutting off the motor), they lowered the pressure of the cooling system from 1.3 bar >>0.9 bar. This lowers the boiling point of the coolant mixture, which is, in my opinion, part of the reason why so many of our cars overheat.

But back to the topic, yes, a cooler thermoswitch should have been part of the cooling system recall. Oops.

-s-

Isnt it behind the coolant filler neck? I guess I just need a pic of its location.

Even then you don't have air flowing over the radiator since the car isn't moving.

Turbo times are to keep oil moving so it won't coke on a hot turbo. The stock turbos are water cooled so they don't have this problem.

Yes, it's on the firewall side of the filler neck. Unless you have girly hands, you'll have to remove the alternator to get room to access it.

Neit:

My fans have only come on once after shutdown. I never really run my car all that hard anyway, but I also have a downpipe, which I believe keeps temps low to begin with. I found, like yourself, that I can get the fans to come on by turning the ignition switch to on. It does seem to do some good if they stay on for 7-10 minutes. But then, I've discovered I can achieve about the same thing by just lifting the hood and letting the heat naturally rise off the engine bay when I come home at night. I really need to get a water and oil temperature gauge to monitor this more closely. I'm looking forward to your experience with the Miata switch. By the way, what is the order number for the Mazda part? My local Mazda dealership had no idea what I was talking about when I attempted to order one. Is the Wells unit comparable?

The part number is: N350-18-840

Hey sorry to hijack the thread.... but, mahjik, does that mean that I can change it without removing the filler neck? Is it a pita to get to?

Yes and Yes.

wait, does that mean the all I have to remove is the altenator and I can get to it? Thanks again for your help Mahjik!!

It's been a while since I did the install. You'll definitely need to remove the alternator and maybe get the pressure chamber out of the way. Basically, once you remove the alternator, remove anything else that is in your way of the sensor. ;)

Thanks Man....

What store is the part number for? Thanks...

That is the Mazda part number. If you go to an auto store, they should be able to cross reference the Mazda number.

Thank you very much!!

Thanks, Mahjik.

questions
 

Is the switch the one on top or the one under it? The one on top has a green connector, look at the pic...

In the second pic is something I found with NO VACUUM LINE connected to it!! It's under the vacuum chamber... Anyone knows what goes there?

The Thermoswitch is the bottom one of the two.

That is only used on automatic transmission RX-7's.

Double Thanks! :D

That was fast!

I found that after i did the fan switch mod my fans started coming on by themselves after shutdown and running for 10 min. I always make sure to drive the car slowly and off boost for at least 3-4 minutes (usually just go slow through the neighborhood towards my house) to allow the engine to cool, so I don't see the need for a turbo timer. When I park in the garage I pop the hood and the fans run by themselves for 10 min. Once I get my water temp gauge I'll have a better idea of how efficient this procedure is I guess.

fan logic, miata switch, recall, etc
 

1) Oem is, with ac off, fans come on slow when ecu's thermo-SENSOR (2-wire) at wp reaches 221F. if heat continues to rise, the 226 fan thermo-SWITCH (1-wire) also at wp turns fans on med speed. no matter how much higher temps rise, fans don't come on at high unless ac is on and 226F is exceeded.

2) miata thermo SWITCH will turn fans on at med speed at 207F for most fd's (not all). the 'slow' speed is then never used when car is running. I think the mazda switch will keep fans on 'till temps drop to 202F, while the autozone will run a bit longer, 'till switch sees 197F.

3) if the recall relay/timer and was added, fans not on at shutdown will come on after shutdown if thermo-sensor sees about 235F+, and run at med speed 'till sensor or switch (not sure which) indicates a lower coolant temp, then fans continue at low speed. max fan time is 10 minutes aft shut down.

Mazda did this to reduce underhood and engine temps. Air drawn thru rad quickly cools stagnent coolant in the thin tubes, and becomes closer to ambient temps. This aft-shutdown fan trip has never happened in my 93 with recall timer, as I use parking lite and fan_mod_switch to keep temps below 210F when driving.

4) by just going key on shortly aft shutdown, heat soak is tripping sensor or switch. miata switch may enable the fans at lower temps, with your manual key-on cool down method.

5) with recall timer and fan-mod switch, switch is set on 2 minutes before shutdown, and left on 25 sec aft shutdown ... key-off. at this point fans are at med speed. then switch is turned off after 25 sec (to avoid draining battery thru fan relay) and speed drops to slow. Lock it up and walk away ... fans continue for 10 minutes, regardless of switch position. Handy when public parking.

This is essentially a testing sequence used by dealer to assure recal mod was done correctly, but very effectively cools all components under the hood after shutdown and locked up. search ciriani/lightning newbe link for test data. For most fd's, turning on the added fan-mod switch will instantly turn on the fans at med, any time engine is running or in key-on mode.

I was able to install teh thermosensor without removing the altenator. But it's a really tight squeeze to get it in. Definitely use some sensor safe sealant if you're unsure of how tight you can get the sensor...

I have a "generic" Miata thermoswitch and with the a/c on mine will switch the fans from high to medium when temp gets down to about 205F.

I know this because I always mist my radiator at the autox and I just spray until I hear the fan speed change. It always switches to medium speed at just over 200F.

UFF!! Finally installed it! Took off the cross-over pipe, pressure chamber and alternator (what a pain to get out) then somehow squeezed the wrench and took it out. I wasn't too tight. It was really bad everytime I had to move a cable (snap, cracle, pop!).

Now to my idea to connect it, I used the stock plug! I pulled out my dremel and modified the Miata switch so it fit nicely in the stock connector.

Things that I would never buy from autozone:

Thermoswitch, Thermostat, and coolant caps.

I've bought these items before and they were faulty. Luckily The thermoswitch and thermostat were on my truck that can take a slight overheating.

Items that relatively innexpensive but are crucial to my engine life I learned to just chalk it up and go to the dealer (malloy) for quality parts.

Thanks now you have me worried! How do i test to see if it's working?

You need an aftermarket temp gauge. Then just warm the car up and let it sit idling (so no air is coming across the radiator). If you see temps around 215F or more and the fans aren't on, it's not working.