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quick electrical question

M

mitsumotors

NAXJA Forum User
Location
Winnipeg
i made the upgraded headlight harness and it works good. only problem is that i have factory daytime running lights here in Canada and the lower voltage that my daytime running lights put out is not enough to keep my relay on the new harness switched on. it just kinda hums and vibrates. so i figure since the power from the one original headlamp wire is not enough to switch it what if i wired both original headlight wires into the relay? then it would be receiving twice the power and should keep the relay switched?
 
It doesnt work that way,it sounds like a voltage drop in the switching circuit(to the relay).Look for bad grounds and corroded wires.
 
here is the general idea. everything in black is what is already there. the red wire is the one in question. can i add this wire and solve my problem?
Untitled.jpg
 
i read somewhere that the voltage coming from the origional headlight harness is supposed to switch the relay to turn on the lights. but when the lights are not turned on and only the daytime running lights are on the voltage they are sending out is not enough to switch the relay properly. i could be wrong though?
 
It seems that you just need to run your wires for the daytime running circuit with the reduced voltage directly to the low beam headlight plugs, if you want to retain that function. But if you are trying to have the dimmer lights for daytime, and are trying to make the relay stay on, the relay will still make the lights run bright as normal, so you may as well skip the daylight running lights thing and leave your lights on both day and night, if it's a legal issue.
 
its more of an issue of not wanting to turn my lights on and then forget them on when i turn the vehicle off. that is the only thing drl's are good for.
 
yup its left and right headlight harness(original ones). i tries doing what i did in the diagram and it didn't work.

hooking the drl's between the relay and the lights would work but i would have to know which wires were which on the drl's harness. my manual doesn't show it.
 
Most automotive relays only have around a 7 volt pull in voltage, meaning that they only need 7 volts to switch. And that's at around only 1 amp. If you add another wire to the relay, you're gunna end up with the same voltage as before. Sounds like you're got a bad relay, not that uncommon.
 
Last edited:
So what must be happening is that the DRL actually uses the same wire as the headlights. It just sends a reduced voltage down the same wire for a dimmer light. This is not enough voltage to pull the relay in. You probably know that with the relay buzzing, you will probably burn it out.

You would have to figure out where the split in the 12V vs. reduced V occurs. You never gave your YEAR to check wiring diagrams.
 
The DRL wiring is included in my 2000 FSM. It looks like only the right headlight operates on DRL. Is that true? If so, running them both off the left side wire should totally disable the DRL. Are you sure you have the left side wire? Do you have the FSM?
 
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