SuperlecDirect - ElectriciansForums.net Electrical Suppliers
This official sponsor may provide discounts for members
Advertisement - Content continues below
Advertisement - Content continues below

Discuss coolant temp sensor > is polarity important? in the Auto Electrician Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:  American Electrical Advice Forum

Does it matter which way you connect the 2 wires to an engine's coolant temperature sensor?
Does the thermistor inside the sensor have polarity?

I do not know the pinouts on the car's temperature sensor and I do not want to risk damaging the car's computer.

Thanks in advance.
 
Wetroom Store - Network Wetroom Suppliers
This official sponsor may provide discounts for members
Advertisement - Content continues below

DPG

-
Arms
Esteemed
Advent Win
A thermistor generally has no polarity, however it may be that there is more inside the sensor than just the thermistor. I doubt it though. Has the sensor got a part number? What make is it and what make is the car?
 

James

-
Mentor
Arms
Supporter
Esteemed
As above, thermistors have no polarity.
However if it is a thermocouple then polarity is important.
It is unlikley to cause any damage but will work backwards, I.e a rise in temperature is seen by the control or gauge as a fall in temperature.
 

Lucien Nunes

-
Mentor
Arms
Esteemed
If you get exactly equal resistance readings on a meter with the meter probes either way round, that fall significantly as you increase the temperature but remain equal, it is probably just an NTC thermistor and polarity independent. If the readings are unequal or do not vary with temperature, then it is either semiconductor based or an NTC with interfacing electronics that will be polarity sensitive.
 

static zap

-
Advent Win
I do not want to risk damaging the car's computer.
Damaging the computer is un-likely ,as
most inputs/outputs are protected from many eventualities...
(un-less already on its last legs)
---
Getting plenty more error codes by loading a supply rail that has several other sensors also attached (More likely) !
 
  • Thread Starter Thread Starter
  • #6
A thermistor generally has no polarity, however it may be that there is more inside the sensor than just the thermistor. I doubt it though. Has the sensor got a part number? What make is it and what make is the car?
Thank you very much for your reply, Zap.

The car is a 2005 Australian Toyota Hilux 2.7L petrol engine model TGN16R

I don't know the part number of the original temperature sensor, but there are several suppliers of replacement sensors, one of which is part number CCS52

My understanding of the scheme is that the Hilux's ECM (computer) supplies a +5 volt reference signal to one of the 2 pins on the sensor and an ECM ground to the other pin. The ECM then monitors changes to the resistance of the sensor.

I have heard that on some cars the coolant temperature sensor has a 2-stage temperature/resistance graph characteristic - I do not know if that implies that there could be more componentry inside the sensor (e.g. diode?)

Thanks.
 

DPG

-
Arms
Esteemed
Advent Win
From what you've said I wouldn't risk it. Can't be certain it is just a thermistor.
 
Test Meter - Forum Sponsors since 2007!
This official sponsor may provide discounts for members
Advertisement - Content continues below

Reply to coolant temp sensor > is polarity important? in the Auto Electrician Forum area at ElectriciansForums.net

uHeat Banner - Forum Discount Available
This official sponsor may provide discounts for members
Advertisement - Content continues below
Top Bottom