Mark Simpson

Build Safer Electrical Systems with Electrical Relays

Mark Simpson
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Duration:   6  mins

Electrical relays are essentially electrically operated switches. They have been used in a wide array of electrical systems for over 200-years. Early classic cars had little need for electrical relays and often even lacked fuses or circuit breakers. As cars became more sophisticated and the electric systems more robust, relays proved an effective means to deliver large amounts of electric current without having to go through a conventional switch.

There are several advantages to using electrical relays when building or adding on to your electrical system and they include: Shorter heavy gauge wire lengths, deliver higher amperage to components, take load off of switches, reduce electrical fire risk. Relays have proven themselves reliable in many automotive applications, including horn, starter and cooling fans. Today most modern cars include dozens of relays for nearly every system on a car.

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3 Responses to “Build Safer Electrical Systems with Electrical Relays”

  1. Scott Westenskow

    Please find an electrical teacher that actually knows what they are doing.

  2. Kevin Koelz

    I understand what he's saying, but for beginners watching this, I suggest being specific about low and high amps, not high and low voltage. Don't call a relay a breaker

  3. David Dare

    RELAYS are the reason why some cars could not shut off. Contacts are notorious for welding themselves together. In the old days, the key switch directly disconnected the ignition circuit and the key would ALWAYS control the ignition without fail. This guy needs to learn the difference between voltage and current. Long wire lengths create a VOLTAGE drop. BTW, the whole car is 12-volts, not low and high voltage. A relay uses a 'controi' signal to energize a 'power' circuit. For instance, the horn relay energizes the relay coil through the steering wheel ring. When the horn is pressed, the relay contacts control the horn power. It's all 12 volts but horn current would melt the steering column wiring and destroy the brush spring without a relay. Because the key switch cannot control power windows, power seats and convertible tops, Ford added a relay that is controlled by the key switch. When the relay coil is energized, contacts connect battery power to the accessories.

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