Making me work are you? I'll just put a flashlight behind it.

 

for the thermo resistor switch...the lower one...is the wire/connector thats supposed to hook up to it coming out of the same "bundle" of wires as the ECU coolant temp sensor?

I don't have anything plugged into mine...but there is a nasty crunchy wire hanging there that "looks" to have been black/red at sometime in its previous life...

I've read all the comments about the miata switch...why not go to something even cooler...like a 195 or 190 degree switch? The thermostat opens at 180...why not try to keep the water closer to that? And if you're constantly triggering the fans to stay on with a manual switch...this would just kinda automate it...right?

john

 

I would love to put a 190 degree switch, but don't know of one that would fit. That would be awesome to keep the temps between the 180-190 range. It seems silly to me that the acceptable range is 180-230. Which is obviously what Mazda set it at. I don't understand why any manufacturer would do this. If 180 is a good warm running temp, why allow it to go to 230, even if that temp can be handled, why do it, it's just going to cause premature wear on many things.

 

That wire is for the thermoswitch. Yours broke off from the connector - mine did this as well. Strip the wire and resolder it to the connector. If you're lucky you'll have enough slack wire on the connector side to use, otherwise you may have to improvise.

 

Does anyone know what the thread pitch is of the sensor?

if you go to napa and be friendly...they'll pull out the sensor book and let you look through it. They usually list the sensor switching temps and the thread pitches.

I found it was pretty hard to find one for my rally car that switched at 180...but I did...I'll see if the threads fit tonight. I got it from summit.

john

 

 

Don't know, but I'd bet 10 mm x 1.25 which is what the IAT sensor is.

 

Any idea why mine doesnt work??? i grounded that wire! and it worked fine but after the first week or so, my blinkers wouldnt work, neither will the horn!

It blew the fuse,after i changed the fuse, the wire i used to do ground the fan literrly melted,
now if i want to connected and cause a electrical shortage, im i plugging the wrong ground wire??

 

ok, I figured I'd post this here as it is as good a place to start as any.

I am doing some cooling mods to my car while I have the engine out. I plan to install a small electric water pump in the heater line that will come on after the car shuts off along with the fans(maybe just one) for a certain amaount of time or till the temp falls below a certain point. While deciding how to wire this up I have looked into the cooling circuit on the scuderia website as well as post here on the forum.

I am considering changing the stock thermoswitch for the miata one as it actiavtes at 205 instead of 226. This will turn the system on if heat soak rises above 205 and turn it off when it falls below. In my attempt to understand the way this interfaces with the fans and the ecu, I have come upon discrepancies with the way people think the thermoswitch works.

DamonB, if you see this post please reply as I find things different from you.

1st) the low speed setting is controlled by the ecu. This is universally accepted. If you look at the wiring daigram you see that relays 2 and 4 are powered on both the coil side and the latch side by constant 12v. It is the ground side of the coil side in both relays that is connected to the ECU as well as the TFA port. The output side of the latch goes to the fan motor which is then gronded. When the ecu is powered and the thermosensor(not thermoswitch) reaches the preset temp point set in the ecu (adjustable in the PFC), the ecu grounds this leg (coil side) activating the latch and powering the fans. You do the same thing when you ground the TFA port. This is low speed.

2nd) Relay #3 is the medium speed relay, since it is operated by the termoswitch (not thermosensor) it is a dumb circuit. It will only activate after relays 2 and 4 are already on as the termoswitch is set to activate at a higher temp than the lowspeed setting controlled by the ECU, unless you set them higher by adjusting this setiing in the PFC. No one would do this! Futhermore, it is not connected to the ECU (at least in the 93 wiring diagram). It is connected to the fan control module which is simply a timer circuit. Further more, it does not supply power to the fans, it only closes an addition ground on the fan motor. If you look closely at the circuit for relay # 3, it has power from battery coiming into the coil side of the relay. the output side of the coil goes to the thermoswitch. when the thermoswitch closes (either 226 stock or 205 miata) it completes the circuit of the coil in the relay by grounding it. this activates the latch side. the latch side has no power going into it. it is gounded on one side and connects to the fan on the other. Therefore it simply connects an additional ground for the fan.

It would seem that you would have to have power coming from relays 2 and 4 for relay three to even do anything. I do not know the layout of the fan motors but it would seem that by suppling a ground on the additional leg, you allow the fan to spin faster. This means that the medium or second speed of the fans is not controlled in anyway by the ECU. The test connector for the fan mod is wired into the same line as the thermoswitch. by grounding it, you simualte the activation of the thermoswitch and if done for more than two minutes, activate the timer circuit in the fan control madule. The fan control module is also connected to the TFA line and must latch this at the same time to power the fans. Once the thermoswitch drops below its designated setting. relay three drops off and only 2 and 4 stay on for the remainder of the 10 min. This is exactly what happens when you flip the fan mod switch off after 30 sec. the fan speed drops to low.

I bet if you activate relay 3 without activating relays 2 and 4 at the same time you will not see the fans come on. The other relay, relay 1 is the A/C relay and is on a different circuit all together and is not important to this discussion.

If I have missed anything please point it out. According to this logic, the miata sensor is just as important to people with power FC's as it is to people with stock ecu's it also means that the ECU only can controll the low speed setting and not fan speed 2 as is implied many times. I do not know why it is even in the datalogit software.

That's all for my rambling.

Mike

 

Read your post and looked at page Z42 in the manual. I have never studied the cooling relay diagrams so closely but my initial look agrees with everything you said. I do know the thermoswitch only triggers high speed as it is a "dumb" switch; it only knows when it's set temp is reached. The ecu controls the other fan speeds by monitoring the thermosensor.

All that said I don't understand the need for such complexity in the cooling fan system. Why 3 speeds? :shrug: If the car is getting used at all in much heat its fan speed is going to be controlled by the hottest temp switch (the thermoswitch; whether it is stock or the Miata part). The ecu controls slow and medium speeds with input from the thermosensor but when things get hot it's the thermoswitch that will always really control things. IMHO that's the only one worth messing with unless you want a different speed for some sort of shutdown function and even then wouldn't you still just use the highest speed available?

 

Wow...there's some great info in this post!

Sonny

 

Okay,

Strangely enough, just Monday, I noticed my fan was on after I turned the car off. This is the first time I have ever noticed this and I would have -thought- the car had been hotter when turned off before.

I was waiting for a tow (clutch went out, with no warning), the car was idling with the A/C on. I cut the car off to go get food after a while, and the fan was still on.

My car was built in January of '92...does that mean it has had an update done?

-C