A faulty temperature sensor in your vehicle can cause your engine to overheat, so if you’re experiencing problems with your car or truck overheating, it’s possible that the sensor is to blame. Fortunately, swapping out a temperature sensor is as simple as plugging in a new sensor cable. However, you should test your sensor first to ensure that it is the source of the problem and that you do not have a more serious problem that needs to be addressed. With your handy multimeter, you can quickly and easily obtain a few readings that will tell you whether or not your sensor is functioning properly.
Part 1 Connecting to the Temperature Sensor
1. Make sure to put your vehicle in park, turn off the engine, and open the hood. To make sure your vehicle is stable and won’t roll, put it in park, and take the key out of the ignition to avoid accidentally shocking yourself while driving. Open your hood to gain access to your engine compartment, and make sure it remains open throughout the process.
If you have recently driven your vehicle, you should wait approximately 15 minutes to allow your engine to cool down to avoid burning yourself.
2. Place your temperature sensor next to your thermostat to ensure proper operation. Follow the upper radiator hose all the way down to the engine. The thermostat housing is located at the end of the hose. When the temperature sensor is installed next to or attached to the thermostat, the temperature sensor appears as a small, black device that is plugged into a wiring harness.
It is possible that the temperature sensor for your vehicle is located in a different location depending on your vehicle’s make and model, but it is typically located on the engine block next to the thermostat.
It is possible that the thermostat will be located behind the metal cylinder on top of the engine block, which is known as the intake plenum, if you are working on a truck with a large engine. To remove the intake plenum without causing damage to your engine, you’ll need to hire a professional.
To locate the sensor if you’re having trouble, consult your owner’s manual or look up your vehicle’s make and model online to determine where it is located.
3. Remove the sensor from the vehicle by unplugging it and removing it from the vehicle. One hand should be used to hold the wire harness while the other hand should be used to pull on the sensor’s body. Gentle slide it out of the harness to avoid damaging any of the wiring and place the sensor on a flat working surface, such as a desk or table, to prevent it from being damaged further.
4. Connect the multimeter leads to the sensor’s outer connectors using the soldering iron. Three connectors, which resemble metal prongs, are located on the plug end of the temperature sensor. Take your red lead and connect it to one of the connectors on the far right or far left of the board, depending on your preference. Then, attach your black lead to the connector on the opposite side of the board from your red lead so that they don’t come into contact with each other.
Connections between the sensor and the wire harness are made using the connectors.
If the leads come into contact with each other, you will not get an accurate reading.
The majority of temperature sensors have three connectors, but some may have as many as five. In any case, no matter how many connectors there are, always connect the leads to the ones on the outside in order to keep them separated.
Part 2 Taking Hot and Cold Readings
1. Fill a small cup or container halfway with ice and water. Fill a clean cup halfway with approximately 6 fluid ounces (180 mL) of clean water and a few ice cubes to bring the temperature down to a comfortable level. Allow for a few minutes to allow the ice to cool the water down before continuing.
Your sensor will use the cold water as a reference measurement to determine its accuracy.
2. Check the temperature of the water with a thermometer to ensure it is 33 degrees Fahrenheit (1 degree Celsius). After a few minutes, take a reading of the water’s temperature with a digital or analogue thermometer, depending on your preference. If the water temperature is around 33 degrees Fahrenheit (1 degree Celsius), you should be fine. If this is the case, wait another 2-3 minutes to allow the ice to cool it down even more before taking another measurement.
3. Start by turning on your multimeter and setting it to direct current. Press the power button on the multimeter while the temperature sensor is still connected to it. This will activate the sensor. If your sensor has a manual dial, look for the DC setting on the dial and turn the dial to select it; if your multimeter does not have a manual dial, look for the DC setting on the display and select it.
The DC setting will provide you with a voltage reading that you can use to check the sensor’s functionality.
4. Take a reading from the sensor after it has been submerged in water. Gentle lower the sensor’s end into the water until the entire device is fully immersed, then repeat the process. Wait for the screen to display the temperature of the cold water, which should take about a minute. Write down the measurement you took as a point of reference once you have obtained it.
When a temperature sensor is placed in cold water, a typical reading is around 5 volts.
Take note that if you aren’t getting any readings from the sensor, you should try removing it and reconnecting the wires to make sure they are properly connected. Once more, try taking a reading; if you still do not get anything, it is possible that your sensor is broken and must be replaced.
5. Another reading should be obtained by placing the sensor in a cup of boiling water. Heat approximately 6 fluid ounces (180 mL) of water in a kettle or a pot on the stove until it comes to a boil. Pour the water into a mug or other container after that. In a pot of boiling water, submerge your temperature sensor and wait a few seconds for your multimeter to register the temperature reading. Make a note of your reading so that you can refer back to it later.
A reading from hot water should give you approximately.25 volts.
Make certain that the cup you use is capable of safely holding boiling water.
Take care not to burn your fingers when working with hot water.
6. Make a comparison between your readings and the recommended readings for your vehicle. A specific temperature sensor is used in each make and model; therefore, when you test them with a multimeter, you will get specific readings. Look up the hot and cold readings of your vehicle’s temperature sensor on the internet and compare them to your own readings to see if they are close to each other. Then your sensor is working properly, and you may be experiencing a problem somewhere else in your system. If this is not the case, you will need to replace your sensor.
For example, if your vehicle’s temperature sensor is supposed to have around 5 volts in a cold reading, compare your measurements to the correct reading to see if they are within a few volts of each other.
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