Posted by APB in Frigid NY on Saturday, November 24, 2007 at 23:24:22 :
In Reply to: wiring a relay switch posted by Jerry in Idaho on Saturday, November 24, 2007 at 22:18:55 :
The only reasons to use a relay are:
1. if the switch contacts won't handle the current draw of the load. (Example - starter solenoid controlled by ignition switch)
2. if the switch controls a different voltage than the voltage required for the load. (Example - thermostat controls oil burner ignition)
3. if the switch is mounted at a distant location, requiring long runs of wire to the load. (Example - thermostat wire is small, power feed to oil burner is heavy gauge wire)
In the case of rear work lights on a pickup, none of these reasons exist. Auxiliary light switches can be purchased that will easily handle the load of the work lights. The switch will be controlling 12Vdc and that's what the lights require. The same length and gauge of wire is required whether you use a switch, or a switch/relay combination. Since the battery supply is up front, there is no savings on wire because the same length and gauge must be run from the front to the rear of the truck.
Oh, and one more thing: the relay will be the first thing to fail, right when you need the lights the most. You will then just temporarily bypass the relay contacts to get the lights to work. This temporary work-around will remain the status quo until you sell the truck. Been there, done that.
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