My RST is running EFI.
The cooling fan is activated by the ECU using PWM control.
Currently the temp sensor is in the inlet manafold (original Ford) but I think relocating it to the oem fan switch location would be better as it’s measuring the coolant at its hottest before going into the radiator.
Any one think why it wouldn’t be a good idea?

 

I would be very surprised if it is using PWM control....moot point anyway.

If it is using the OEM coolant temperature sensor location, then clearly it is fine there.

 

My point really is the the oem position for switching the fan is in the thermostat housing and presumably there for a reason?

The temp sensor for the ecu is in the inlet manifold, I’m using this to control the fan.

Looking at other engines (Honda B series) they have the ECU sensor in the thermostat housing.

I just wondered if there was a reason Ford done it this way and would be “better” moving it.

The temp reading on the ECU is quite unstable switching the fan on/off as the cross hairs move between boxes in the table.

It has a Maxx ECU it allows used defined PWM outputs that I configured and use a MK 2 Focus controller.

 

Ultimately you're maintaining an average temp anyway.

When you say unstable, in what regard ? under what circumstances ? Most temp sensors are very slow responding anyway, so naturally damp out things.

The ecu temp sensor would need to be within the engine so to speak, engine block, head etc are all good spots, where water is always circulating. Beyond the T-stat, this may not always be the case, although with the engine warm, there would almost always be water moving even on the rad side. Not so much during initial warm up

 

“When you say unstable, in what regard ? under what circumstances ? Most temp sensors are very slow responding anyway, so naturally damp out things.”

It jumps around +/- 3-4 degrees but this is enough to switch the fan erratically.
I have always thought It was “noise” but can’t see a filter in the Maxx to dampen it.
This is what lead me to wanting to move the sensor, but think your correct in that the sensor can’t respond that quickly.

Back to the drawing board. 🥴

 

Again, can you provide a log or graph ?

If it's jumping fast, ie. large changes in less than say 0.5 or 1s, then it has to be noise.

Water temp sensors are very slow to respond, so they simply cannot change that fast, and any transition would be a smooth change, not a jump. So is that graph smooth, or literally jumps ?

 

Just to be 100%, you're reading values off the grey sensor above the aux air valve, not the brown thermo-time switch? As the latter could be throwing you right off..
(Colours based on OE, so may have changed if running any aftermarket sensors)

 

Never took a log but it is moving quickly so must be noise. I will log it and send it to Maxx.


“Just to be 100%, you're reading values off the grey sensor above the aux air valve, not the brown thermo-time switch? As the latter could be throwing you right off..
(Colours based on OE, so may have changed if running any aftermarket sensors)”

The temperature sensor is in the OEM position for a Fiesta RST, I don’t have the thermo time switch or auxiliary air valve stuff.

 

Always log, it's a vital tool

 

The unstable temperature feedback is now fixed.
Found my TPS to be faulty, TPS and coolant temp share the same reference voltage.