most Coolant temperature sensors
These voltages are not accurate with anything other than a 1k pullup
| Vehicle | 0C | 20C | 40C | 50C | 60C | 70C | 80C | 90C | 100C | 110C |
|---|---|---|---|---|---|---|---|---|---|---|
| Most Japanese | 4.26v | 3.57v | 2.93v | 2.86v | 2.55v | 2.23v | 1.92v | 1.67v | 1.40v | 1.18v |
| Most Aftermarket | 4.26v | 3.57v | 2.93v | 2.86v | 2.55v | 2.23v | 1.92v | 1.67v | 1.40v | 1.18v |
| Most German | 4.28v | 3.60v | 2.78v | 2.43v | 2.12v | 1.84v | 1.60v | 1.20v | 0.75v | 0.56v |
| Most Ford/Chevy/Dodge | 4.26v | 3.57v | 2.78v | 2.45v | 2.12v | 1.59v | 1.36v | 0.97v | 0.75v | 0.60v |
The adjacent chart shows most common coolant temperature sensor data as well as other aftermarket brand sensors (GM Delphi, AC Delco, AEM, NGK, MOTEC NTC, etc). This information has been pulled from multiple manufacturer diagnostic manuals and converted from the OEM 2.2k pullup for my 1k pullup, but should still be double-checked for accuracy. It's important to use the approprirate pullup with the voltages on the chart when inputting in your engine management (unless you are wiring in your own, in which case, pick either 1k or 2.2k). 1k ohm pullup resistors provide a faster response to the ECU, but the difference in speed is negligible.
most air temperature sensors
The adjacent chart shows most common coolant temperature sensor data as well as other aftermarket brand sensors (GM Delphi, AC Delco, AEM, NGK, MOTEC NTC, etc). This information has been pulled from multiple manufacturer diagnostic manuals and converted from the OEM 2.2k pullup for my 1k pullup, but should still be double-checked for accuracy. It's important to use the approprirate pullup with the voltages on the chart when inputting in your engine management (unless you are wiring in your own, in which case, pick either 1k or 2.2k). 1k ohm pullup resistors provide a faster response to the ECU, but the difference in speed is negligible.
These voltages are not accurate with anything other than a 1k pullup
| Vehicle | -10C | 0C | 10C | 20C | 30C | 40C | 50C | 60C |
|---|---|---|---|---|---|---|---|---|
| Most Japanese | 4.42v | 4.26v | 3.98v | 3.57v | 3.26v | 2.93v | 2.86v | 2.55v |
| Most Aftermarket | 4.42v | 4.26v | 3.98v | 3.57v | 3.26v | 2.93v | 2.86v | 2.55v |
| Most German | 4.44v | 4.28v | 3.99v | 3.60v | 3.16v | 2.78v | 2.43v | 2.12v |
| Most Ford/Chevy/Dodge | 4.66v | 4.26v | 3.95v | 3.57v | 3.43v | 2.78v | 2.45v | 2.12v |
temperature switches
Wiring: These have one wire or two wires. If using a 2 wire switch one wire should connect to ground, the other connects to your ECU input, relay ground, or bulb. 20 or 22 AWG wire works well. If the switch is only 1 wire, the case of the sensor is the ground, and the other wire is the "on/off" ground signal.
Functions: Since this is a temperature switch, when the desired operating temperature is reached, the switch inside opens or closes. This can trigger a cooling fan to turn on, or trigger a high oil temperature warning light.
Custom uses: The coolant temp switch can be wired into a fan relay to trigger it on when the coolant reaches a certain temp if you run out of outputs on your engine management and you want to use the fan output to control something else..
THREE WIRE TEMPerature SENSORS
Function: The signal wire senses the voltage/resistance variations across the other two wires, and depending on whether the sensor was designed to output the signal wire outputs the voltage/resistance that is converted to pressure, temperature, or position in the ECU. This specific sensor in the adjacent picture is a Bosch PST-F_1 4 wire combination pressure/temperature sensor made for fuel pressure/temperature. It functions the same as a normal 3 wire temperature sensor, the extra wire is for a pressure signal. Be careful purchasing any sensor, and make sure the threads match what your vehicle accepts. The PST-F1 in the adjacent picture has m10x1 threads, others have 1/8 NPT thread and some are even 3/8 NPT.
5 volt power and sensor ground wires. Both of these wires connect directly to the 5v power and the sensor ground from your ECU, or whatever device is receiving the signal.
Signal wire: This connects directly to the ECU
Troubleshooting: If the sensor is showing 0v, check your signal wire or 5v connection. If it is showing 5v, check your sensor ground connection.
