What is an Auto Electric Relay?

An auto electric relay is an electromechanical or electronic device through which a heavy load can be switched ON & OFF with a nominal input of current & voltage.

 How does a relay work?

A heavy electrical load drawing heavy current can be switched on & off by applying a small amount of current through a coil (solenoid). The coil gets magnetized with the current and attracts or repels a plunger (a rod passed through the coil). The attracting or repelling of the plunger either connects two switching contacts in the auto electric relay (also known as NO or Normally Open/Single Throw/Form A) or separates them (NC or Normally Closed/Double Throw/Form C), as required. As soon as the electric source to the coil is stopped, the electro magnet ceases to function and the main contacts go back to their original position. In automobile applications, relays of different configurations with single or multiple contacts are used for different applications.

 Why is an auto electric relay required?

Apart from switching a circuit with heavy load, on & off, a relay is required to 1. Conserve energy 2. Prolong the life of device 3. Improve the efficiency of a device. For example let us take the switching of two headlamps of an automobile. If the same is switched on through a normal switch at the dashboard, the voltage drop from the battery to the lamps through the switch will be enormous and the heat generated in the circuit due to resistance will be considerable. The heavy current will be drawn by the lamps which will not only heat the circuit but also drain the battery heavily.

 To give an example of the effect of voltage drop, a chart is given below:

Operating Voltage.        Luminous Intensity of a Lamp. 100%                                      100% 95%                                        83% 90%                                        67% 85%                                        53%   To switch on a 12V-60/100 Watt Halogen lamp, a typical 12V Relay allows a voltage drop of only 0.02V and the coil current is only 2 milliamps.  Another important function of the auto electric relay is quick switching off (0.05Sec Max.). The more time the contacts of a switch take to break at full load, the more spark will be generated due to the electromagnetic effect on contacts in a switched on state. Prolonged sparking will mean more wear of the contact points and the danger of contacts melting and generating a fire. International standards have very stringent auto electric relay specifications. The endurance of a relay is generally specified in millions of switching operations.

 Where should an auto electric relay be installed?

Wherever manual switching has been used for direct switching of a Lamp or Motor or any gadget exceeding 10 Amps of load, a suitable relay must be put in the circuit. It is best if the relay can be kept as near as possible to the load (but not in a hot area surrounding near the engine) Some examples of auto electric relay use may be relays used between the owner operated window switch and the actual motor that moves the window up and down.  Another example  would be using an auto electric relay between the computer and the radiator fan or the A/C compressor.  Also between the computer and the door locks, when the computer is programmed to lock the doors when the car goes in a forward gear.

 How should a relay be installed?

1. Wires connected to the manual switch should be connected to any Coil terminal of the auto electric relay. 2. The load should be connected to any one contact terminal of the auto electric relay (unless Positive/Negative are specified) and the other to the positive terminal of the battery (for Negative Ground circuit), with an appropriate Fuse.   There is an easier way to fix auto electric problems.  Call Pops Auto Electric in Central Florida, they have been handling the hardest and most complicated auto electric problems for many years and they are the acknowledged experts in the field.  Many other shops and dealerships come to Pops Auto Electric when a really complicated electrical problem arises, because they are the best around.  Auto electric relay problems are a snap with Pops Auto Electric, call today:

Call Pops Auto Electric now and put your mind at ease!

407-857-8579

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