Can anyone identify this coolant sensor on an automatic FD? A part# would help since the dealer is having troube figuring it out.

Thanks

 

The FD has three engine coolant temperature sensors, which one are you needing?

One is mounted below the oil filter and behind the oil pressure sender. This one only feeds the instrument cluster temperature gauge.

The second is mounted on the top of the block under the alternator and is the one used by the ECU for engine temperature, basic control of the cooling fans, etc.

The third sensor is mounted on the thermostat housing and signals when the engine is overheated. The manual usually refers to it as the ‘Engine Temperature Coolant Switch’. Unlike the other two whose resistance to ground changes with temperature, this third unit is a simple on/off switch. It turns ON at about 243 degrees F and signals the ECU resulting in an increase to the speed of the cooling fans and probably changes to mixture and timing; all to help cool the engine.

 

i thought the one on the thermostat housing was simply a low coolant light....

 

That's the one on the front of the housing (coolant level). The one on the back of the housing is a temp sensor.
I disagree with the on/off statement. The signal from this sensor is analog. The service manual shows temp ranges relative to the resistance. Part of signal is being used for idle control. I found this out the hard way when the plug was switched between the fuel temp and coolant temp during new engine installation.

 

Trexthe3rd is correct that the sensor on the front of the thermostat housing is the level sensor, and the one on the back is the temperature switch.

As far as I've been able to determine, this switch only shows up in the later revised versions of the shop manual that inlcude the cooling system update. I have a scanned copy of that page that shows this to be a on/off switch, but can't get the image to post without an error. If you want a copy just send me a PM or e-mail.