Aftermarket Fog Lights: Auto-off w/ High Beams?
 

Hey folks, I've got a 2003 Chevy Blazer LS that I've installed some Hella 550 Fog lights on.
Jumping right to the question to try and avoid complicating things: has anybody had any luck in wiring fog lights that automatically shut off when the high beams are turned on?

My switch for the fog lights receives power from the low beam positive, but it seems the low beam sockets continue to receive power when the high beams are on, even though the low beams turn off. Doesn't seem possible?
Not really a big deal, just curious if I may have wired something wrong. Definitely a novice when it comes to vehicle electrical but I managed. My fogs work great other than this one minor gripe.

I've done the mod you want on an 05 TB/EXT and two GMT800 pickups and it's both easier and harder than you think. I also make this installation for friends and neighbors --- but I need more information in the end ...

Your "parking lights" are really getting a digital signal to operate at somewhere around 80-85% power ON, digitally.

You sound like you've tapped into the output to the factory DRLs (what you call "parking lights"} and are stealing a partial voltage trying to run your new lights.

What you need to do is forget tapping into an existing light circuit, as you can see, because you're confused by the voltage remaining on the side of the DRLs all the time. It does --- remain that, that is --- but I don't want to dazzle you with technology.

You're using a DVM or DVOM - right? It won't "see" the digital signal as it cannot switch fast enough for the numbers to stay on the front of the meter.

You need to use a relay --- 4 pin/30Amp/12V automotive style (a very common/standard relay) to tap the power at the relay that controls your fog lights --- these are usually the lights that run below the bumper --- hopefully you have that particular calibration.

I'm assuming a lot here without knowing the way the front of your vehicle looks right now --- can you post a couple of good pixs? - I need to see what lighting calibration your vehicle has now and I can do that if absolutely necessary by the RPO --- but pictures are quicker.

Remember that everything but the paint job and the composition of the wiper blades are computer controlled and you have to outsmart the system so it doesn't throw a hissy.

Thanks so much for taking the time to respond!
So, as far as I know, I don't believe I'm tapped into the DRL circuit. The fog lights will properly turn on along with my headlights when the headlight switch is set to ON (and not running lamps-only position).
I just find it very odd that the low beam sockets continue to receive power despite the bulbs being off when the high beams are switched on.

Here is a little diagram I made to explain how my fogs are wired.
Edit: I should clarify that the switch in the diagram is a dedicated switch just for the fog lights, not the headlight switch.

https://cimg2.ibsrv.net/gimg/blazerf...220da752b0.png

I have to apologize—I think I missed your point and gave a pretty dumb and unhelpful answer.

You're right that they're tapped into the DRLs (I suppose there's no way for them not to be if I'm spliced in the headlight circuit (again dumb answer on my part).
It seems I was wrong that the lights properly turn off when I shut my headlights off. My fogs just work all the time. However, replacing the DRL relay with a modified one that disables the daytime running lights results in my fogs shutting off along with the running lights. In both cases, the fogs still remain on when the brights are on. This is all really not a big deal of course, but I don't mind trying a method you may suggest to make them work properly if it's not too much hassle.

Here's a pic of the front of my truck I also failed to include.

https://cimg4.ibsrv.net/gimg/blazerf...05599b4cd3.jpg

If the low beam light still has power on positive 12v side when bright lights are on then it switches and loses ground when high beams are selected . You should be able to connect your fog light relay coil’s ground in your circuit to the low beams ground wire to make fog lights work with low beams only . The rest of your wiring stays the same

Ah that makes sense. I'll give that a try. Thanks!

Think about it for a minute ---

The DRLs - which you seem to not use because you manually turn your lights ON/OFF to suit your needs ... are a digital signal that is ON about 80% and OFF 20% - resulting in a decrease in observable brightness.

Grabbing power there could cause problems --- maybe the PWM generator will have a hissy --- or not --- but it's not a good gamble.

I suggest you use the DRLs as they are designed and stop manually turning them ON and OFF; then we can have a little more intelligent conversation and find a way to run aux lighting as you like --- and I have done.

But ---> I am a staunch user of the DRLs as a safety factor to keep people from passing on a long straightaway and they cannot tell the distance available --- and when they see my DRLs, they know a car is in the opposing lane.

DRLs are not to help you see --- they are designed to help other drivers see you. Win-Win.

Lemmee know what you want ...



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