Lighting Harness Hack

[Klaatu55]

Morning All,and today's question is. Just recently put in new lighting harness. Of course I have the high beam remaining on with low beam problem. That is low beams work or high beams work. Upon switching back to low beams,high beams stay on. I believe I saw a diode cure with bulb receptacle wire somewhere. But I recently saw an article where if you were not using your factory installed fog lights you could just remove the fog light relay from the PDC and call it a day. Can anyone verify this for me. And correctly state the diode hack so that the fog lights can still be used. Thanks

[Klaatu55]

Is this the wrong forum for this question? Should It be moved to general?

[NW99XJ]

No I think your in the right place.
Interesting problem.
It DOES sound like a voltage-back-feeding issue.
What you'll want to do is diode isolate the high beam feed from the low beam feed near or at he switch. This will be in the wiring harness that comes down the steering column.
Use a good rated (larger) diode, as these circuits have higher amperage.
A diode will have a stripe on one side of it...this is the cathode....the anode will be the opposite side.
Diodes STOPS both a NEG(-) signal and a POS(+) signal from going in a certain direction....depending on the placement of the diode.
(taken from www.the12volt.com)
http://images.the12volt.com/images/12voltdiodes.gif

You would essentially jumper the two leads with the diode, having the cathode side on the lead that goes hot (+) when the low beams are turned on. This will prevent voltage from back feeding to the high beams until the high beams are turned on.

The headlight harness kit you got SHOULD have taken this into consideration and would have had some sort of diode isolation at the relays. Not knowing which harness you have, or how it was hooked up, I can only speculate that it was an incomplete kit, and not installation error.

Hope this helps. Good luck!

[Klaatu55]

It was the Putco kit from Amazon. From what I understand,this happens only on the jeeps like mine (1999)that have OEM fog lights installed. I have read a couple of tips to get around this. The one I used is to remove the fog light relay from the fuse container (the hood) completely,since I never repaired or used my fog lights. The other was to put a reverse bias diode (i think a 1N4001) in series with the remaining unused headlight cable wire to ground. But I can't find that thread again and am not sure of the exact instructions. Not critical at this time so the search goes on. Thanks for your help.

[NW99XJ]

Hmmm....
My kit is virtually identical.
AND I HAVE a 1999.....only difference is I dont have the factory fogs.
I'm gonna have to do some research on this one.

[bluedragon436]

I am very interested to know more on the diode work around... but I might pull my fog light relay for now, as my fog lights are full of mud and useless anyways... I have the LMC trucks harness... and have the same issue of the brights staying on after going back to low beams.. I have to completely cut the headlights and marker lights off to get them back to low beams....

[Klaatu55]

I can confirm that pulling the fog light relay is a quick fix. Still hunting for the article on the diode fix that will allow the fog lights to continue working as designed.

[bluedragon436]

Well I guess I'll pull the relay when I get back home... that way I can flash my brights at people that think they are already on... and not have to turn off my lights completely to get the low beams back... Look forward to seeing the article if you find it... that way I can use the factory wiring for the fog lights to hook up to a set of aftermarket lights and still make use of the factory switch...