Need urgent answer to tapping wiring harness for adding headlight relays.

[Kilroy]

Sorry if this is elsewhere, but I can't find it.



I'm adding relays to headlights on 04. 5. Tapped wire in headlight switch for lows and works fine.



Tried to tap wire for high just above headlight socket. When I checked voltage at this socket, without a bulb in it registered 3 volts with or without headlight switch on. Decided to try using anyway. It will not signal high beam relay to come on. Followed schematic by Stern, seems like everything should be ok, except where to trigger switch. If I put bulb in original socket it works normally.



Suggestions appreciated.



Thanks

 

[p-Bar]

You need to put a resistor across the high beam to ground and also on the low beam. The 3 volts you see is checking for impedance to turn on the bulb . Does that make sense?

 

[Kilroy]

So, besides using the wire to switch the relay, I also run a resistor from it to a ground?

You need to put a resistor across the high beam to ground and also on the low beam. The 3 volts you see is checking for impedance to turn on the bulb . Does that make sense?

 

[p-Bar]

Yes I would do a search on the internet and you should find what you need. If I have time today I will try to ohm out my resistors.

 

[Kilroy]

Thanks. Will have to go with what I have for now. Leaving for MI UP in a few minutes.

Yes I would do a search on the internet and you should find what you need. If I have time today I will try to ohm out my resistors.

 

[Kilroy]

My Solution

With needing to get something done soon, what I did was tap into the only hot wire I could find switched by the headlight switch. This is the wire leading to the dash display lights. I added a rocker switch for the lows next to the headlight switch which goes to the low beam relay. Because I couldn't get the high beam stalk switch to work (got info on resistors too late), I added another rocker switch for the high beams on top of the column near the 4 way flasher switch.



Headlight switch will turn lights on and off normally. I can leave lows to just come on and off with headlight switch, or highs, or both, or just highs. Light output is significantly greater (especially with both on) and I can keep both high and low on together. Sounds kind of mickey mouse, but worked well for evening of driving. Not quite as convenient as normal switching, but completely bypasses (almost) computer controls. As lamp out light was already coming on because of LED's I used for taillights, there is not difference with that. If light bothers me, that's what black tape is for. High beam rocker switch is lighted which acts as an indicator light.

 

[SWithrow]

If your using the stock headlight wiring the negative pin will not handle the current of both HI and LOW beams, it will eventually burn up the negative pin on the connector and bulb.

 

[Kilroy]

If your using the stock headlight wiring the negative pin will not handle the current of both HI and LOW beams, it will eventually burn up the negative pin on the connector and bulb.

I've totally bypassed the stock wiring, including running a new ground straight to the battery, one for high and one for low, #12 wire for everything.

 

[SWithrow]

Hope it works for you. When I did the Hi Low modification to mine, I found out the negative pin on the stock bulb would not handle the current draw of both filaments being on at the same time. I even upgraded the headlight plugs to a heavy guage wire but still was burning up the negative pin on the bulb. I decided to install 4 55watt driving lights on my brush guard.

 

[cerberusiam]

I've totally bypassed the stock wiring, including running a new ground straight to the battery.

That is not a highly reccommended solution. Grounding an add-on component straight back to the battery is playing russian roullette with the sensitive electronics. Grounds should always be made to engine or chassis ground points, not the batteries. You can introduce noise into the electrical circuits, or, worst case back feed power and burn out relays in the FCM, TIPM, ECU circuits.