Fan question:

[mtdoragary]

Does thermostatic switch directly turn on the fan, or does the switch tell the computer to turn on the fan?

 

[NancysToy]

It works through the ECM.

 

[mtdoragary]

It works through the ECM.

So, if I fit a 195 degree switch, will the computer comply and switch on the fan at 195 degrees? Or if I fit a 185 degree switch, will the computer comply and switch on the fan at 180 degrees?

 

[NancysToy]

So, if I fit a 195 degree switch, will the computer comply and switch on the fan at 195 degrees? Or if I fit a 185 degree switch, will the computer comply and switch on the fan at 180 degrees?

I doubt it. Things aren't usually that straight-forward with a CanBus system. The signal has to match what it is expecting. You'd have to try it, but you risk ECM damage.

The temp switch goes to the ECM, which triggers the cooling fan relay, which starts the fan. I'd use your sensor (or a switch or a fan controller) to trigger a separate relay, pulling in the fan. Be sure to use the same power source, to avoid shorts. You might be able to trip the existing relay in parallel, by grounding the relay coil, prior to the ECM, but it could cause interference or module failure.

 

[lightman02]

So, if I fit a 195 degree switch, will the computer comply and switch on the fan at 195 degrees? Or if I fit a 185 degree switch, will the computer comply and switch on the fan at 180 degrees?

There are a couple types of temp sensors. One is a switch type that will close to at a set temp but they are commonly used in non-fuel injected systems to turn on things like cooling fans directly when there is no computer. When it comes to the Spyder because it is fuel injected the sensor is resistive I believe also know as a thermistor. The same sensor that gives you the temp reading is the same sensor that tells the computer to turn on the fan. Basically the type of sensor and software in the spyders computer is set so as the resistance of the sensor changes (from coolant temp change) it corresponds to a particular temp scale in the software. That input is reflected on you temp gauge bars and when gets to a certain level the fan will kick on as that is what the software is programmed to do. You could try to fool it with adding a resistor but that would also offset the actual coolant temp reading.

 

[mtdoragary]

I doubt it. Things aren't usually that straight-forward with a CanBus system. The signal has to match what it is expecting. You'd have to try it, but you risk ECM damage.

The temp switch goes to the ECM, which triggers the cooling fan relay, which starts the fan. I'd use your sensor (or a switch or a fan controller) to trigger a separate relay, pulling in the fan. Be sure to use the same power source, to avoid shorts. You might be able to trip the existing relay in parallel, by grounding the relay coil, prior to the ECM, but it could cause interference or module failure.

Thanks; a separate controller and sender seems the way I should go.