Help! 2006 f250 overheat mystery

[Sequoiha]

Yes, I watched it on the laptop, the engine was not hot, just the pocket the switch sits in,

[boscoe99]

What is an ECT?

[Sequoiha]

What is an ECT?

Really, says the guy with 3000 posts giving advice, smh!

[rodbolt17]

Engine Coolant Temperature.

[fairdeal]

"ECT"

confusing to see that term

since the switches at the thermostats look to be much more DIRECTLY representing the "coolant"

whereas the temp sensor "only" indirectly

[rodbolt17]

the ECT is a negative coefficient sensor.
the temp switchs are just that.
a discrete on or off switch.

[fairdeal]

my point was just that at the thermo housings
its "looks" obvious that the water flowing through is directly acting on the switch

whereas the sensor - IIRC - is jammed into a "projection" of the casting that - from the outside - isn't obviously "close" to the "water jacket"

that's all I'm saying

[fairdeal]

I'm thinking of the auto engines I played with as a kid - if you unscrewed the temperature sensor - coolant would run out.

[boscoe99]

Now I know. Thanks for the education.

It is what Yamaha calls a thermosensor. AKA engine temperature sensor. I just have never heard it referred to as an ECT sensor before.

Just seems strange to me to call it a "coolant" sensor. Coolant being water in this case. Which boils at nominally 212 degrees F at sea level.

The sensor trip point for sounding the alarm is well above 212 degrees F. 248 degrees F actually. Well above the boiling point of water.

I would have guessed that it was measuring the temperature of the block and not the coolant. Good that I am not a betting man.

[James1234]

I appreciate the comments and the advice. I am going to get a status update today and, if not diagnosed, will start asking questions based on what has been discussed here. I'll keep you all posted.

[rodbolt17]

Boscoe.
the ECT triggers nothing.
it only supplies engine coolant temp information to the ECU for fuel trim.

the temp SWITCH'S trigger the alarm.

its not uncommon when the plate or ex stack fails to see hot temp switchs with the ECT in the normal range.

[boscoe99]

Boscoe.
the ECT triggers nothing.
it only supplies engine coolant temp information to the ECU for fuel trim.

the temp SWITCH'S trigger the alarm.

its not uncommon when the plate or ex stack fails to see hot temp switchs with the ECT in the normal range.

The confusion was that I had never heard the F250 thermosensor referred to as an ECT sensor. Now I know.

But the NTC termistor/thermosensor/ECT sensor will trigger the over temperature alarm if and when the temperature rises to the point that the resistance of the sensor is lowered to the point that the ECU sees this as the over temperature point for the block position that is being measured. Although technically the ECU is looking for voltage which varies as a function of the resistance changing which is a function of temperature.

Yes/no?

[rodbolt17]

the ECT wont and cannot set an alarm .

that's the function of the switch's.

[Sequoiha]

The confusion was that I had never heard the F250 thermosensor referred to as an ECT sensor. Now I know.

But the NTC termistor/thermosensor/ECT sensor will trigger the over temperature alarm if and when the temperature rises to the point that the resistance of the sensor is lowered to the point that the ECU sees this as the over temperature point for the block position that is being measured. Although technically the ECU is looking for voltage which varies as a function of the resistance changing which is a function of temperature.

Yes/no?

No, when the pink wire on the thermo switch is grounded it sounds the alarm,

[fairdeal]

here's the section from the SM on testing the thermoswitch -
apparently it closes (presumably triggering the alarm) at 183-194 F
makes sense - pretty hot water

but - isn't there something in the YDS about a temperature of 248 F ?