Leon

Activate your Ebay fog lights with the auto feature of the headlights.

I bought a set of lights with harness off Ebay and was happy with the way they installed, but wasn't thrilled with the wiring. The way they are stock out of the box, power from the battery goes though the fuse and to a relay which supplies power to the fog lamps. The relay is turned on by the under dash switch. Why have a relay at all? The switch doesn't do as good of a job handling the current needed by the lamps, and it allows us to modify the wiring to turn the lights on and off with the low beams.
The first diagram is the stock wiring as I received the lights. Not shown is the ground wire (black) going to the switch for the pilot lamp in the switch. The only current going through the switch is the relay current, but you have to turn the lights on and off each time.
The second diagram differs in one point. The red wire going to the switch was found inside the harness and cut. This wire was extended and routed up to the front of the car, where it was connected to the low beam passenger side lamp wire. This wire is Tan with a White stripe and was easy to see after removing a little of the outer black wrap. Be careful not to nick any other wires. When connected to the Tan with a White stripe wire, if the Fog Lamp Switch is on, whenever the low beams come on the fog lamp relay will get power turning on the fog lamps. When the BCM turns the headlights off, the fog lights will also go off.
The reason the relay is connected to the low beam is because in many areas it is in the vehicle codes that the fog lights be activated only when the low beams are on.
The wiring may differ on the lights you get, but the principal is the same. Use the headlight power to turn the relay on, which turns the fog lights on.

Leon

To make things a little simpler, I drew another diagram. Basically what this mod involves is cutting the red wire that goes to the switch and taping it (there is still 12V on that wire). Run a new wire from the bottom terminal where the red wire was to the headlight circuit, I used the Tan/White wire in the harness above the radiator. There are other places to hook this, but the Tan/White wire was the easiest without having to disassemble anything, just removing a little of the harness wrap and splicing in.

mixman

There are several different fog lamps available on eBay. Which brand & model are you talking about?

Leon

I think there is only one vendor selling the stock lights with a wiring harness. Try this item Fog Lights
The others on Ebay are the "Bling Lights" that are not an OEM fit like these are.

mixman

I bought a set of THESE and they fit quite nicely. A basic wiring harness is included with them however, beit this set or that, my LS Panel still requires OEM wiring between the switch, relay, fuse box and computer if I want to use the auto function.

mixman

Do you know where I can get aftermarket OEM wiring?

Leon

You might see if the dealer can order the wiring. The install that I did doesn't require the computer, and allows the lights to turn on whenever the low beams are on rather than having to turn them on evry time as is needed with the stock HHR setup. The harness you got with the set you have should be able to be used, connect the relay signal to the low beam circuit as I described and they will work every time. I bought the set I have because they snap into place like the OEM lights and didn't require and modification to mount them.

mixman

Hmmm...So if I want the ability to use fogs with both high and low beams, would I need to splice into the parking lamp wiring? And would doing so eliminate the need for a new switch?

Leon

Yep. But one thing to consider is the law. In many states the vehicle code states that fog lights only be lit with the low beam. That's the reason I tied into the low beam circuit.