Car TipsNot Working

Rear View Mirror Temp and Compass Not Working

If you have a car with a rear view mirror that displays the outside temperature and/or the direction of travel, you may find it frustrating when these features stop working. Not only do they provide useful information for your driving experience, but they can also indicate underlying issues with your vehicle’s electrical system. In this article, we will guide you through the steps to diagnose and fix rear view mirror temp and compass not working, organized under the following headings:

Understanding Rear View Mirror Temp and Compass Systems

Before you start troubleshooting, it’s helpful to know how the rear view mirror temperature and compass systems work. Most rear view mirrors with these features use a built-in sensor that detects changes in temperature and magnetic fields. The sensor is connected to a microprocessor that processes the data and displays the readings on the mirror. The microprocessor may also have some programming that compensates for variations in the sensor’s accuracy due to factors such as altitude, speed, and local magnetic anomalies.

Checking Power and Ground Connections

The first thing to check when your rear view mirror temp and compass are not working is the power and ground connections. The mirror may have a separate power source, a fuse, or a relay that controls its function. You can consult your car’s owner manual or a wiring diagram to locate the relevant components. Use a voltmeter to measure the voltage at the mirror’s power supply terminals and the ground connection. If there is no voltage or a low voltage, check the corresponding fuse, relay, or wiring for damage, corrosion, or loose connections. Sometimes, the problem may be as simple as a blown fuse or a loose wire.

Testing the Sensor and Microprocessor

If the power and ground connections are intact, the next step is to test the sensor and microprocessor. Depending on the type of mirror you have, the sensor may be located inside the mirror housing, on the outside of the car, or elsewhere. You may need to remove the mirror or access the sensor through the grille or the dashboard. Once you locate the sensor, use a multimeter to check its resistance or output voltage as you expose it to different temperature or magnetic conditions. The sensor’s readings should correspond to the expected values, as specified in the mirror’s manual or technical data. If the sensor is faulty, you may need to replace it.

The microprocessor that processes the sensor data and displays it on the mirror may also fail due to internal or external causes. To test the microprocessor, you can use a diagnostic tool or a scanner that can communicate with the mirror’s control module. This tool can read the error codes stored in the module’s memory and interpret them to identify the specific malfunction. Sometimes, the microprocessor may need reprogramming or replacement if it’s damaged or outdated.

Calibrating the Compass and Temperature

Even if you fix the underlying issue with the rear view mirror temp and compass system, you may still need to calibrate the compass and temperature displays. Calibration ensures that the readings are accurate and aligned with the actual conditions. To calibrate the compass, you need to drive the car in a circular or figure-eight pattern, following the mirror’s instructions, until the compass stabilizes and shows the correct direction. To calibrate the temperature, you need to expose the sensor to a known temperature source, such as a cup of ice or a warm object, and adjust the mirror’s calibration settings accordingly.

Why is my rear view mirror not working?

If your rear view mirror is not working, there could be several reasons for this. One of the most common issues is a faulty power or ground connection, which can prevent the mirror from receiving power or signals from the car’s electrical system.

Another possible cause is a malfunctioning sensor or microprocessor that detects and processes the outside temperature and compass direction. These components can fail due to damage, corrosion, or software glitches. In some cases, the rearview mirror may need to be replaced if it’s irreparable or outdated. To diagnose and fix the specific problem with your rearview mirror, you may need to follow some basic troubleshooting steps or seek professional assistance.

How do I turn on the compass in my rear view mirror?

To turn on the compass in your rearview mirror, you first need to ensure that your vehicle is equipped with a compass feature in the mirror. If so, you can usually activate the compass by pressing a specific button or a combination of buttons on the mirror itself. Check your car’s owner manual or the mirror’s instructions to locate the compass button and the corresponding symbols or LEDs that indicate the compass mode.

Depending on the mirror’s make and model, you may be able to switch between different compass modes, such as the heading, the cardinal direction, or the bearing. To ensure accurate readings, you may also need to calibrate the compass by driving the car in a circle or following specific instructions until the compass stabilizes and shows the correct direction. If you have difficulty turning on the compass or calibrating it, you may need to consult a professional technician or the mirror’s customer support.


Rear view mirror temp and compass not working can be a nuisance, but with some basic troubleshooting techniques, you can diagnose and fix the problem. By checking the power and ground connections, testing the sensor and microprocessor, and calibrating the displays, you can ensure that your rear view mirror functions properly and provides.

Rachael McAdams

I'm Rachael, CEO of AutoGeeX, bring unrivaled expertise and passion to the automotive industry. With extensive knowledge and a deep understanding of cars, she shares captivating tales, invaluable insights, and practical tips with readers. As an active presence in the car community, Rachael ignites excitement, revolutionizing the automotive landscape with AutoGeeX's pursuit of perfection.

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button