I want to wire in some spotlights on a 2008 Dodge Ram.
The problem is it has daytime running lights which cannot be unplugged, can only be unprogrammed by the dealer.
The DRLs put a pulse width voltage to the high beam so I can't just use the high beam to flip my relay, I didn't really want to cut a switch into my brand new dash.
Is there a way to have the relay only switch with the high beam input and not be affected by the DRL voltage ?
Have you tried to install a relay on the high beam? Depending on the duty cycle of the PWM signal it may not be enough to energize a relay when only the DRL are on.
Another alternative would be to use a low pass filter like this: https://www.ontrak.net/pwm.htm
You would then have to add a comparator circuit to look for a voltage significantly higher the the voltage produced by the DRL. The comparator circuit would consist of a two input comparator chip (one input to the output of the low pass filter the other to your reference voltage created by a voltage divider or pot. The output of the comparator chip would have to drive a transistor that can drive a relay.
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Kevin Pierson
I haven't tried it yet but I had the same thing on an old Dodge Dakota and it the relay would buzz for a while then click on, I don't want to risk any problems in a new truck with more complex electronics (doesn't have any relays, or done by chips I think).
I think I will put a switch in the cabin to turn off the high beam supply to the relay when the lights aren't on.
the way to do it is to tie into the switch at the steering column it gives you 12v and with a 6 poles 3 position switch you can have high beams trigger or manual trigger works good had to do it on many cop trucks
forgot to mention always use a relay to isolate your cuircuit from the factory one especially on the dodges
For a simple solution, you can trigger a relay by hooking one side of the coil to the parking lights and the other to the low beam headlights. When you turn on the high beam lights, the lows go off, and the coil is energized by the parking lighs and grounds thru the low beam.
I think I get what you mean, instead of grounding the relay coil as you would normally do I run that relay pin to the low beam supply and that way the relay will not energise with the sidelights alone.
Just need the clarifiaction as I have only wired relays in the normal grounded fashion before.
Thanks