On/Off/Automatic Driving lights
 
This project is not as hard as it may look. The idea is to run your driving lights using the high beams as a control. You can disable the lights, turn them on manually, or have the driving lights follow the high beams.

The automatic mode is a must for highway driving, because the driving lights go on/off with high beams. Manual on is handy for off road or lighting a campsite without the headlights having to be on for them to work.

If you use KC Day Lighters or some other high powered lights: See schematic below!

 
Using 55W Driving Lights
This diagram shows the wiring using a Bosch relay. These are found just about everywhere.
 
 
Using 100W+ Driving lights
Don't use a Bosch relay to directly power the lights. Use it to operate a continuous duty solenoid instead. Do NOT use a starter solenoid, because it will burn up in minutes if left on.

A pair of 150 Watt KC's will draw about 24 amps for the set. A bosch relay is rated 20/30 Amps, but the contacts will weld closed due to the high startup surge of about 50+ amps. Use a 50 amp breaker inline with the solenoid also.

Note: with any lightbulb, the filament has a low resistance until it heats to white hot. As it heats up, the resistance becomes higher, and the bulb draws less current. The watt rating is with a heated and operating bulb at the rated voltage. This is also the reason most bulbs fail when first turned on. The startup surge will actually create a high magnetic field and move the filament around as it heats up. The current surge and sudden movement is what causes failure of the bulb. After hours of use, the filament gets fatigued and prone to breakage.

 
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