I installed an FC thermoswitch yesterday, and the wire that came out of the connector on the stock one literally fell apart in my hand, leaving just a little stump to re-attach to. I managed to get a new wire on there, but had some difficulty getting anything to crimp onto the stump. The fans turn on, but I'm worried about the life of the connection.

So now I'm thinking, what happens if the connection fails? Is the default position "fans on"? I hope it would have been designed that way.

 

The fans will not come on if the wire comes off, untill the ecu turns them on. If you have acess to a datalogit you can set the fans to what ever temp you'd like You should be able to fine a connector in good condition at a junk yard.

Paul

 

Ok, where does the ECU get its information to turn the fans on, if not from the thermoswitch? I thought that was its function? Perhaps I misundertsood.

 

Thermosensor.


Here's is information from FD3S.net: http://www.fd3s.net/fan_mod.html

When the relays come on:

* Relays 2 & 4 controlled by PCME, come on when temp reaches 221F.
* Relay 3 controlled by thermoswitch, comes on at 226F
* Relay 1 controlled by A/C switch.

How fan speed affected by relays:

* Off, none on
* Low speed comes on when relays 2 & 4 are active.
* Med speed comes on when 2 & 4 are on plus _either_ 3 or 1 comes on but not both
* High speed comes on when all are on.


If the Thermoswitch isn't working, then one of the ways for the fans to come on at Medium speed is lost. It indicates that all must be one for High so you probably loose the ability for the fans to run on High all together.

 

Ok, well then something screwy is going on with my FD. I ran the car up to operating temp yesterday to ensure that the fans would turn on, and they did. However once they turned off, I turned the a/c on to see if they would come back on, and they did. So by turning the a/c on and off I could turn the fans on and off, not low to medium, as is suggested by the link.

I have a friend who insists that there are two fans, one for a/c heat exchanger, and one for the radiator. I told him I didn't think so, I thought there were two fans, and both were either on or off. Can anyone clarify?

 

Also, according to Dale Clarks FC thermoswitch thread: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/its-official-do-not-buy-miata-thermoswitch-until-you-read-397156/ the fans should now come on at 210F. Mahjik, your link indicates that the fans still should not come on until 221, but they will come on at medium speed, because relay #3 is already active.

What gives with the conflicting information?

I put an FC thermoswitch in, I was expecting fans to come on at 210°F!

 

Condition #2 would be reached before condition #1. Therefore the thermoswitch kicks the fans on sooner. The original programming has the thermoswitch temperature higher than the thermosensor limit, therefore there is no way for condition #2 to exist without condition #1 originally.

Using a lower temperature thermoswitch basically breaks the original sequence of events.

 

As the list is written, there is still no way for condition 2 to exist without condition 1. Condition 2 basically says "Condition 1, + relay 3 or relay 4". If I'm understanding you correctly now, that list should read:

How fan speed affected by relays:

* Off, none on
* Low speed comes on when relays 2 & 4 are active. or when relay 3 is active
* Med speed comes on when 2 & 4 are on plus _either_ 3 or 1 comes on but not both
* High speed comes on when all are on.

 

The real question is will the thermoswitch trigger medium level all the time or not (i.e. without relays 1 & 2 on or not), or does it only trigger low when 3 is the only relay on. That I don' t have the answer for.

 

You've failed me Mahjik!! Nooooo!!!

Anyone have an answer for this one?