An idea for AUTO headlight and AUTO Fogs
Thread Starter
Super Member
Joined: Jun 2005
Posts: 811
Likes: 5
From: Bay Area
08' S550, 04' E320 4matic, 03' Acura TL-S 6 speed, 1968 Vespa P150
An idea for AUTO headlight and AUTO Fogs
I brought this up awhile back seeing how the fog light switch can't permanatly be left in the on position so we don't have to switch it on all the time. I don't there I've ever driven without the driving lights on. But I also like the idea of it being on automatically along with the headlights.
Anyways, I'm thinking of adding a relay tapped onto the headlight and taping it directly into the fogs. I will also install a switch inside the cabin so I can manually switch the fogs off when I'm sneaking somewhere. Just the same way as you would install an aftermarket fog on any car.
Do u think that it will hurt anything if there is power tapped into the fog light lights when the main switch is off?
BTW: here's an example of what I can use
http://cgi.ebay.com/ebaymotors/Pre-A...QQcmdZViewItem
Anyways, I'm thinking of adding a relay tapped onto the headlight and taping it directly into the fogs. I will also install a switch inside the cabin so I can manually switch the fogs off when I'm sneaking somewhere. Just the same way as you would install an aftermarket fog on any car.
Do u think that it will hurt anything if there is power tapped into the fog light lights when the main switch is off?
BTW: here's an example of what I can use
http://cgi.ebay.com/ebaymotors/Pre-A...QQcmdZViewItem
Super Member
Joined: Sep 2004
Posts: 551
Likes: 2
From: Virginia
2005 Carlsson CD32 E320 CDI Inline-6
Don't hijack electrical stuff on your Benz
Its just not a good idea. You may be overloading a circuit and be left in the dark or worse when you least expect it.
If you cause a relay to overload it will get hot and could lead to contagious failure of other nearby relays, fuse blocks, etc. What if a short results and you fry an expensive module?
Just put up with it, I think you'll experience less pain in the long run.
If you cause a relay to overload it will get hot and could lead to contagious failure of other nearby relays, fuse blocks, etc. What if a short results and you fry an expensive module?
Just put up with it, I think you'll experience less pain in the long run.
Thread Starter
Super Member
Joined: Jun 2005
Posts: 811
Likes: 5
From: Bay Area
08' S550, 04' E320 4matic, 03' Acura TL-S 6 speed, 1968 Vespa P150
The way I see it is, when the fogs are off, there is no contact on the switch. I'm guessin'g it'ss a dpdt relay, now the only other issue I see is that in the auto mode, when u disarm the alarm @ night fogs come on, this will also turn on the headlights. 
could be a good thing. I don't see how you can overload the rely, you're running 2x wire parallel you're just increasing the guage. 12v is still 12v, amperage is bassed on the load not the output of the battery.
could be a good thing. I don't see how you can overload the rely, you're running 2x wire parallel you're just increasing the guage. 12v is still 12v, amperage is bassed on the load not the output of the battery.
Thread Starter
Super Member
Joined: Jun 2005
Posts: 811
Likes: 5
From: Bay Area
08' S550, 04' E320 4matic, 03' Acura TL-S 6 speed, 1968 Vespa P150
I've also thought of this, I believe this sensor can only read the bulb when the switch is on. The sensor checks for broken circuits hence to tell when there's a blown bulb. By doing this, nothing is being cut.
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Joined: Apr 2005
Posts: 666
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From: Boston, MA USA
03 E320 -wife's car now; 07 Porsche Boxster S - my toy
You may want to find an inductive coupler to sense when there's current flowing the in the low beam circuit (to detect the light-on, not the sealing current that checks the bulbs), and then have that coupler hook into a relay which would supply current to the fog lights. You will also need some diodes to prevent the fog light current from coming back thru when the light switch for the fogs is actually turned on.
I thought about doing this on my E320 a couple of years ago and started drawing out a schematic, but I got lazy and dumped the idea.
Regards,
paul...
