Relays (headlight)

[Warren Lovell]

Okay, what is the purpose of the relay? What does it do? Whay do you need one? I need to know this stuff guys!

Thanks,

Warren

 

[cranetruck]

Repeating (copied from earlier thread):

A relay is a electromechanical device, which uses a low current coil (electromagnet) to move contacts, which in turn can control much higher currents.
On the deuce, all lights are controlled by the 3-lever switch on the dash. It has a built-in circuit breaker rated at 20 amps.
When extra lights are added, such as marker/clearance lights, this circuit breaker may run close to capacity and just stepping on the brakes or turning on the turn signals may trip it. Suddenly you have no lights at all until the circuit breaker resets, which may take a minute or so.

To prevent this circuit breaker overload, a relay can be used to handle the heavy loads and only the coil current runs through the 3-lever switch.
Circuit is shown below along with an actual relay installation (2nd image).

I have also added a relay in the turn signal circuit to reduce the chance of blowing out another flasher unit.

 

[Warren Lovell]

Thanks for the diagram. What if you use a seperate switch? Do you still need a relay?

warren

 

[cranetruck]

You can certainly use a separate switch alone with its own circuit breaker (like the "override switch" in the diagram).
The reason for the relay is to leave the control of the headlights with the 3-lever switch.

 

[Pappa-G]

I put a set of 28volt 500watt (total) lights on my truck. I wired seperate from the headlight circuit. I used a "constant on" type relay for a snowplow set up. It cost about $11.00, a 24volt relay from a golf cart cost $65.00. So far they seem to work fine. I originally had tried using an old FORD solinolid but that quickly fried (it was not a constant on type). I hope this helps. ~ Pappa-G

 

[marksgarage2]

Constant on solenoids are also used on electric winches. They are very bulletproof. I use them on all my performance motors. Even at 220 they will start right up. A constant off will not. Good unit.