Wiring the fog lights to come on with headlights

[Mr. B]

I did this mod with the diode. It worked like this, no fog lights with the DRLs, fogs on automatically with low and high beams.

The diode burned out, so I replaced it with a straight piece of wire. Now it works like this, fog lights on with the DRLs, fogs on automatically with low beams, no fogs with high beams.

I don't get it. Does anybody have any idea what may be going on? I don't want the fogs on with the DRLs. I may just pull the wire and deal with how it was stock. Or, is the a more robust diode I could use?

 

[BigRed76]

what you're experiencing is the exact way it is intended to work ..... as far as I know

 

[dheadv8q]

Get yerself a relay that can be adjusted for pickup voltage. Adjust the relay to pickup when the voltage is higher than the DRL voltage.

 

[Mr. B]

Just had a chat with one of my EE buddies here at work. The 1N4004 diode is rated at 1 amp. He believes that is the problem. Depending on the wattage of our fog lights, the diode probably needs to be in the 3-5 amp range. Therefore, we are burning out the 1 amp diode. I see on the Radio Shack website that the offer a 6A-50V diode. I'm going to buy a pack of those and give it a try again.

He also said it is fine to run diodes in parallel, so if one is in there and gets hot, you can add another one and see if that helps. My guess is I'll be fine with the 6A diode.

 

[007fl]

If you were using the diode to control the relay it should have been fine. The relays don't draw that much. But your buddies right, you can just parallel several diodes to lower the load on each and keep them cool.

 

[Mr. B]

I could have swore the fogs stayed on with my high beams before. They don't now, with the diode or straight wired.

 

[stevek]

I could have swore the fogs stayed on with my high beams before. They don't now, with the diode or straight wired.

The fogs turn off with the high beams, they aren't intended to be on with them. In two 07 Tahoes, an 08 Yukon, and an 09 Denali they all do the same - I doubt it's an error.

 

[jdub5256]

I think what he is trying to do is overide that so that when he turns on the high beams the fog lights stay on as well. I did this same mod its in a write up somewhere on here. but mine was fine i would turn the truck on at night and low beams come on plus the fog lights but when i would turn on high beams the fogs would stay on as well as low beams plus high beams. but at that time the diode would burn right up. took the diode out and ran a straight wire no more probs. during the day drl's are on at night low and fog lights come on when i hit high beams all lights are on it works great.

 

[BC Lightning]

The fogs turn off with the high beams, they aren't intended to be on with them. In two 07 Tahoes, an 08 Yukon, and an 09 Denali they all do the same - I doubt it's an error.

Unless you add the wire, I jumped my fogs with a wire and no diode (used a diode at first and burned right up) and my fogs come on with my low and hi beams

 

[Zed 71]

The fogs turn off with the high beams, they aren't intended to be on with them. In two 07 Tahoes, an 08 Yukon, and an 09 Denali they all do the same - I doubt it's an error.

He is jumping the fuses to have the fogs on automatically with low/high beams.

Mr. B, check that the jumper is connected to the right fuse and also the right prong on the fuse. If your fogs are 55W then you need a 5A diode at a minimum. Keep us posted.

 

[Mr. B]

I have a Denali, not a Tahoe, I wonder if that is the difference. You guys have separate bulbs for low and high beam don't you?

 

[stevek]

I have a Denali, not a Tahoe, I wonder if that is the difference. You guys have separate bulbs for low and high beam don't you?

Yeah the Tahoes have separate bulbs, we however are stuck with these stupid H13's. I believe they have 9005 or 9006

I mean I suppose you could just put a few diodes straight into each the high and low beam wires and connect them to the fog lights. You can use a vampire clamp and wire it up and use Plastidip to waterproof it... it's easier than taping or shrink tubing it.

 

[Zed 71]

I have a Denali, not a Tahoe, I wonder if that is the difference. You guys have separate bulbs for low and high beam don't you?

Ah, I didn't notice you had the Denali. Yeah I am not sure how those low/high bulb are wired/controlled.