I have a question on the resistance-check of coolant temperature sensors.
BACKGROUND:
The L81 manual says that at 15 Deg Celsius (59 Deg F), the sensor should ohm between 4114 Ω and 4743 Ω.
PROCEDURE:
1) I measured the temperature of my work area, and it is about 80 Deg F (26.6 Deg Celsius): Notice how I selected the use of the Fahrenheit scale because it is the one used on the vehicle.
2) I calculated the range between the reference 59 Deg F (average 4428 Ω's) and a high operating temperature (i.e. 250 Deg F), and the result is 75 Ω per degree of temperature change above 59 Deg F.
3) I measured the actual work area temperature at 80 Deg F . This translates to a calculated change in ohms of 1575 Ω (75Ω TIMES 21 Deg F in Change of temperature). In other words, when the sensor detects a temperature rise of 21 Deg F, the average resistance drop should be 1575 Ω's lower than the reference for 59 Deg F, so the Ohmmeter should be able to read 4428Ω MINUS 1575Ω WHICH EQUALS 2853Ω's.
RESULT:
However, when I ohm the original sensor, I get 2.269 kΩ or 2,269 Ω's.
TROUBLESHOOTING:
A) I went to Auto Zone, and I purchased a replacement sensor (complete with new pigtail for the harness for just under $18 dollars).
B) I measured the resistance on the new sensor, and I get approximately 5 Ω's less (2.264 kΩ indicated) at the same temperature when compared with the original sensor.
c) I measured the resistance between the case (the outside metal portion of sensor) and the center pin on the original sensor , and the ohmmeter reads approximately 10.500 - 11.000 MΩ resistance (MILLION OHMS, RIGHT?).
D) I did the same measurement on the replacement sensor, and the ohmmeter read infinity between either pin in the sensor and the case.
OBSERVATIONS:
What I see is that the replacement sensor reads very closely in ohms to the original sensor.
I also see approximately 11 million ohms resistance between the pin and the case of the original sensor, but there was infinity resistance between either pin and the case of the replacement sensor.
QUESTION:
Is my approach sound, and if so, then is the original sensor bad or defective?
GerryLP:cool
BACKGROUND:
The L81 manual says that at 15 Deg Celsius (59 Deg F), the sensor should ohm between 4114 Ω and 4743 Ω.
PROCEDURE:
1) I measured the temperature of my work area, and it is about 80 Deg F (26.6 Deg Celsius): Notice how I selected the use of the Fahrenheit scale because it is the one used on the vehicle.
2) I calculated the range between the reference 59 Deg F (average 4428 Ω's) and a high operating temperature (i.e. 250 Deg F), and the result is 75 Ω per degree of temperature change above 59 Deg F.
3) I measured the actual work area temperature at 80 Deg F . This translates to a calculated change in ohms of 1575 Ω (75Ω TIMES 21 Deg F in Change of temperature). In other words, when the sensor detects a temperature rise of 21 Deg F, the average resistance drop should be 1575 Ω's lower than the reference for 59 Deg F, so the Ohmmeter should be able to read 4428Ω MINUS 1575Ω WHICH EQUALS 2853Ω's.
RESULT:
However, when I ohm the original sensor, I get 2.269 kΩ or 2,269 Ω's.
TROUBLESHOOTING:
A) I went to Auto Zone, and I purchased a replacement sensor (complete with new pigtail for the harness for just under $18 dollars).
B) I measured the resistance on the new sensor, and I get approximately 5 Ω's less (2.264 kΩ indicated) at the same temperature when compared with the original sensor.
c) I measured the resistance between the case (the outside metal portion of sensor) and the center pin on the original sensor , and the ohmmeter reads approximately 10.500 - 11.000 MΩ resistance (MILLION OHMS, RIGHT?).
D) I did the same measurement on the replacement sensor, and the ohmmeter read infinity between either pin in the sensor and the case.
OBSERVATIONS:
What I see is that the replacement sensor reads very closely in ohms to the original sensor.
I also see approximately 11 million ohms resistance between the pin and the case of the original sensor, but there was infinity resistance between either pin and the case of the replacement sensor.
QUESTION:
Is my approach sound, and if so, then is the original sensor bad or defective?
GerryLP:cool
