Engine Coolant/ Air Temperature Sensor (off car)

engine coolant/ air temperature  sensor

www.elise-shop.com

the coolant and air temperature are the same and are both a NTC type (negative temperature coefficient), this means that when the temperature rises, the resistance in the sensor will lower. this means that is will send a higher voltage to the ecu when the engine gets hot (operating temperature).
Generally there is a 5 volt input to the sensor and when the engine is cold, the output to the ecu is around 1 volt, when the engine is at operating temperature it is around 4.5 volts.

www.wiringdiagrams21.com

The 2 prongs on the sensor are a earth and a 5 volt input (doesn't matter which)
This works by changing the voltage output the the ecu receives by changing the resistance as the temperature changes.

TESTING COOLANT TEMP SENSOR
to test this sensor i heated up some water in a bowl starting at 33°C and ranging up to 75°C.
as the temperature increased i measured the resistance between the two windings of the sensor which was decreasing as it got hotter.

i then recorded some data at different temperatures of the sensor:

Water Temperature	Resistance
33°C	1.36 k ohms
35°C	1.33 k ohms
40°C	1.14 k ohms
45°C	0.96 k ohms
50°C	0.78 k ohms
55°C	0.68 k ohms
70°C	0.46 k ohms
75°C	0.39 k ohms

HTML Tables

TESTING AIR TEMP SENSOR

when i tested this sensor i also got a bowl and heated up the water, i started at room temperature and then put it in the bowl which was up to 55°C.
to measure the resistance i put my ohmmeter on the two prongs of the sensor and recorded my readings:

Temperature	Resistance
room temp	1.81 k ohms
35°C	1.57 k ohms
40°C	1.23 k ohms
45°C	1 k ohms
50°C	0.87 k ohms
55°C	0.71 k ohms

HTML Tables