Hi All,
(2007 Mazda 6 Diesel Hatch)
I'm having an interesting time attempting to wire in a set of aftermarket driving lights and could use some help.
To summarize, for the kit, I need to find a wire that is hot only when the high beams are on. This will be used to fire a relay that runs the driving lights.
My problem is that the high beams on this car are switched on the earth side. From the high beam bulbs perspective, +12V is supplied always to the hot wire. The ground wire switches between +12V and earth when you switch from LO to HI beam. At low beam, the +12V in the ground wire equalises the voltage drop over the bulb so that it stays off.
So... what to do?
If I tap the earth wire, I get the inverse of what I want. A live wire on low beams and an earthed one on high beams.
If I tap the hot wire, the lights will be on regardless of high or low beam selection.
Thoughts?

 

Use the negative feed from the highbeam to pin #85 and have Pin#86 & Pin#30 as12v+ feed from the battery. Pin#87 is your output to the driving lights.

Basically you use pin# 85 & 86 as the triggers/switch, which needs a positive & negative feed, doesn't matter where it comes from.


Conventional Relay setup

 

I realize that one potential solution is to use a relay. Wire the coil in parallel with the high beam light. Relay is closed whenever the light is on.
Question is: should I use a resistor in series with the relay coil? If so, can you recommend values and wattage?
I have a few leftover resistors from wiring in LEDs (120 ohm 25W I think). I really don't want the current to pick the easy way through the relay rather then the bulb.

 

No need for a resistor

 

Almost exactly what I had in mind, just not sure whether to wire in series with existing hi beam or in parallel.

 

Just tap into the high beam wiring at the plug.

 

Parallel it is then.
Thanks for the input, I'll get started after Supercheap opens tomorrow.
I'll update when I get it working.