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On/Off/Automatic Driving lights

Article by Craig Ueltzen

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.

With any lightbulb, the filament has a low resistance until it heats to white hot. As it heats up,

the resistance becomes higher, & the bulb draws less current. The watt rating is with a heated &

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 & move the filament around as it

heats up. The current surge & sudden movement is what causes failure of the bulb. After hours of

use, the filament gets fatigued & prone to breakage.

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	Lighting & Electrical Projects &/or Demons in Your GMC
Some Good Wiring Advise	The Bosch Relay Unraveled	Improved Headlight System
6066 GMC Front Park Lamp Info	1960-1963 GMC Park Lamps Rewire	1964-1966 GMC Park Lamps Rewire
Installing Driving Lights	Installing Fog Lights	Installing Cornering Lamps
Improved GMC Backup Lights	Rear Fog Light Project	GMC Trucks Cargo Lights
Fuel Gauge Trouble Shooting	HeadLight Trouble Shooting	Park/Tail/Stop Light Trouble Shooting
Wiring a Volt/Ammeter	Custom Instrument Panel	Turn Signal Systems
Electric Cooling Fans	Install the Delco-Remy 12SI Alternator	Trans Temp Gauge
	Wiring Diagrams

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