Signs of a Bad Relay Switch

by Paul ParsonsUpdated March 16, 2018
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Image by, courtesy of Lenore Edman

Relay switches are responsible for causing an action through an electrical current. These devices are found in a number of machines, vehicles and other equipment. They are commonly found in cars and are implemented to do a variety of tasks. They are used with automatic windows; they are also used for headlights, air conditioning and other car functions that require circuitry. When things begin to go awry in your car, you may want to identify if the problem is related to a bad relay switch.


In the instance of a relay switch in your car that operates your headlights, you will be able to recognize that the relay switch has gone bad and is in need of replacement or it is being overloaded if your car's headlights are dull or weak. The inadequate amount of light produced means that the electrical current coming from the car battery and to the headlights from the relay switch is not strong enough.


If you notice that your car's automatic windows are not working properly or not at all, this could be due to your relay switch. When the relay switch becomes too congested with dirt or other material, it will not work and your windows could be stuck or unable to move properly. You can sometimes take the relay switches out, clean them, and then reinsert them into your car; however, sometimes they are old and overworked and you need to buy a new one.


You can find out if your relay switches for other functions of your vehicle are not working properly by doing a simple test. Remove your car's dashboard, as this is the main site of the relay switches, and then turn your car on. By putting an end of an alligator clip to a grounded spot, you will then touch a wire of the relay switch with a multimeter. Record the measured voltage, and if it is not the right amount, then your relay switch is working poorly.

Identifying Features

Similarly, when you now turn off your car and look to find if between the electrical device and the relay switch there is continuity then your relay switch is not working well. You can test this again with the multimeter. This method works just as well if the relay switch is found in your home; instead of turning on the car, simply turn on the corresponding switch you suspect may be a problem.


If when driving your car you notice a burning smell, or if your car will not turn on at all, these are signs that your car's relay switch operating the fuel pump is not working properly. If you further note that the relay switch is ever hot when you feel it, these are sure signs you are in need of a new one. You can have the fuel pump relay switch's connectors tested at a mechanical site to be certain; but if you experience any of these warnings, you are best to get a new relay switch.

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