Can you connect a relay to the headlight wire?

Is there a problem connecting the positive wire from a headlight into a relay?  I am trying to setup my aftermarket driving lights so they come on with the ignition but turn off when the headlights are turned on.

I have a spare socket on my fuse box for the igition on power supply, so that part is not problem.  What I thinking might work was adding a Bosch 30amp relay under the hood.   First thing I added was a diode between pins 85 and 86 (prevent inductive kickback). 

Pin 30 goes to ground.

Pin 85 goes to the positive (hot) wire of the headlight.

Pin 86 goes to ground.

Pin 87 not used.

Pin 87a goes to ground wire leading to the Aux light's relay.

Note: I am using a Painless Aux relay wiring kit.  The kit instructions are to connect the red power from the relay directly to the battery, the black wire from the relay goes to ground.  Blue wire goes to the aux light switch.  The red wire on the switch goes to fused positive and the black wire on the switch goes to ground.  I am keeping this same setup except placing the Bosch relay between the ground wire of the Aux Relay and true ground.

Will this work?  Will it affect the brightness of the headlights,  Is there any problems with using a 12V (up to 20 amp) wire to energize the relay?

i have answered many questions today and the standard starter kill relay setup works for a lot.

here is how it is done.

pin 85 connected to the positve wire of the headlights loacated at headlight harness.

pin86 to constant ground

pin 87a to a possitive 12 volt wire that turns off with ignitons preferable place is to look in fuse panel

there is things to buy that can add a fuse to the panel in seconds. get one works with large and mini fuses

put a ten amp fuse in that.

pin 30 run to possitive wire of driving lights

your done test it turn ignition on and lights should go on . while ignition is on turn on headlamps and driving lights will go off

email me for help djfearny2@aol.com

Can I add on to this question/answer?  I just want my headlights to come on through an AUX channel from my alarm.  Can you explain how to wire a relay to do this?

THANKS!

Is this the correct hookup for just controlling the headlights with a AUX channel on the remote?

• 87  ==  12v+
• 85  ==  Ground
• 86  ==  AUX channel
• 30  ==  Headlight + wire
• 87a =   Not used

Hey CP...  Actually you'd probably use +12V on pin 85 as AUX outputs usually output a GROUND pulse.  However unless your AUX output on your alarm has a feature for "latching" that will only turn the headlights on momentarily (for a "pulse").  Some alarms have a feature in which the aux output stays on as long as you hold the button so in that case you'd get them to be on as long as you held the button.

If your alarm does not feature latching (and you want to turn the lights on with one press and off with the 2nd press) you need to get a latching relay and hook it up the same way.  The only thing is that with the latching relay the relay energises and rests in the "on" position on when the button is pressed once.  Energising the coil a 2nd time will "unlatch" or turn "off" the relay thus extinguishing the lights.

Finally if you could get a Time-Delay relay (or use an appropriate capacitor), you could make it so one button press will activate the lights and stay on for a few seconds or minutes and then go off automatically.