if your not blowing fuses then i cant see any point in a relay. Relays in this configuration are just a heavy capacity switch that is activated by the main horn button. The benefit of this would be to not destroy the factory switch if the unit your installing takes more current than the old horn. But they suggest to do it anyways so why not try hooking it up. good learning experience. relays seem complicated but they are really simple. manufacturer had good instructions on their site
A relay is used so a light duty switch can activate a heavy duty circuit. Your horn button is a light duty button and the new horns draw some big power. You might want a relay.
Blowing fuses and using a relay have nothing to do with each other. You need to have a fused power source to the relay. A relay does not make the circuit draw any less amps. A relay is used so a light duty switch can activate a heavy duty circuit.
A relay is used to split a circuit into two parts.
Part 1 is the control side of relay. Terminals 85 and 86 have an electromagnet coil between them. When the coil is energized (meaning power and ground are supplied to the terminals) the relay connects terminals 30 and 87 together turning the relay "on". The power draw across terminals 85 and 86 is measured in milliamps
. This allows any type of switch or the use of an ECU to activate the circuit without having to worry of it burning out.
Part 2 is the load side of the relay. Depending on your relay, there are either 4 or 5 terminals on it. They are labeled 85, 86, 30, 87, (and 87a if 5 terminals) If you have an SPST (single pole single throw) relay then you have 4 terminals; 85, 86, 30 and 87. If you have a SPDT (single pole dual throw) relay then you have 5 terminals; 85, 86, 30, 87 and 87a.
85 and 86 are used for turning the relay on and off. 30, 87, and 87a do the work and handle the amps. This is the heavy duty switch part. 30 and 87a are connected together when the relay is off. When the relay is turned on, 30 and 87a break connection, but 30 connects to 87. Turn the relay off again and 30 and 87 disconnect; 30 reconnects with 87a.
If there is no 87a terminal then it is just a single connection between 30 and 87 being made and broken.
You can use your factory horn button for your new horns, but you might burn the button out since it is not made to handle the power draw of the new horns. Using a relay, you can use the factory switch to activate the relay, which handles the power for the new horn.