Universal Car & Motorcycle Horn Trumpet Relay Harness with BOSCH Relay




What is an Automotive Relay?

Automotive relays of different sizes are found in every type of land or sea vehicle. They are often used to enable a low amperage circuit to switch a higher amperage circuit on or off. An example would be turning headlights on. Automotive relays also allow items to switch at the same time by using a single output, therefore allowing one to simultaneously open and/or close continuity on multiple items.

Why is a relay required??

Apart from switching a circuit with heavy load, on & off, a relay is required to

Conserve energy
Prolong the life of device
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 relay is quick switching off(0.05Sec Max.). The more time the contacts of a switch take to break at full load, the more sparks will be generated due to 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 relay specifications. The endurance of a relay is generally specified in millions of switching operations.

Item Specification:

  • Fit any H4 H/L Headllamp
  • 600 Watt Maximal
  • With BOSCH Relay
  • Plug n Play
  • 2 Output for Left and Right Headlight



Additional information

Weight 0.5 kg
Item Condition



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