I read an article about 2 years ago on the benefits of daytime running lights. The NTSB gave them high marks for assisting drives to see a vehicle more easily. Anyway, I bought a 1983 300SD and I thought about trying to hook up the fog lamps as daytime running lights. I know, purists are cringing about now. So here is how you do it if you are interested.

The process started with the fuse box, which is under the hood on my model. I looked at the inside cover of the fuse box and saw that fuse #14 was a 25 amp, it was for the rear defroster and heated seats (which I don’t have) so it had amperage to spare. I tested the fuse with a voltmeter and found it was hot only when the ignition was fully on and was cold when the ignition was off, perfect. There are two recessed screws toward the front of the fuse rack, remove them and gently pull the fuse rack up. You can then locate the screw connection for fuse #14. I took some 12 gauge wire, crimped a connector to the end and removed the connection screw to #14 fuse and put the wire on it and screwed it down. I then ran the wire through the side of the box (snip one of the rubber grommet and put the wire through). I ran it through the firewall (again through a grommet) and brought the wire into the engine compartment proper. I put a toggle switch on a bracket near the firewall that wasn’t used for anything. I ran the wire to it and connected to one side.

Now, at the headlight assemblies there is a 4-prong plug that is the connection for the fog and headlights. After much testing I found that pin #1 was the hot for the fog lamp. I decided to hook up the drivers side first. I put a splice box on the wire and connected that to the toggle switch I had installed. With my fingers crossed I tested the “running lights”. To my surprise BOTH fog light came on! I tested everything with a voltmeter to make sure I had not created a voltage back flow or short. I also tested all my electric apparatuses in the car to make sure they worked. I even turned on the fog light with the switch inside the car (albeit they were already on) and all was fine. I check all the fuses in the fuse box and all were fine. I made sure that the wires were not over heating also. Everything was just fine.

So, I have been driving for a week and have not had any problems with the set up. The running lights give the car a newer look when it’s going down the road. I did it for safety reasons and I am glad I did. It makes me feel better when my wife and kids have that little bit of extra protection.

And for all the purist out there, all I have to do to return it to stock is flip the toggle switch under the hood and the whole set up is neutralized.

All of this is for what it’s worth………….

Every Mercedes I've ever owned had daytime running lights. All I had to do was turn the light switch two clicks to the right. The best part is that my solution, like yours, was not mandated by the government.

Have a great day,

Good point Larry. The trouble for me is my wife said she wanted to have a no-brainer solution. I told her turning the switch was a no-brainer and she wasn't amused...LOL

Yep, I like it too that I did it on my own free will.....

You know, they say that DRLs make you more visible in the daytime, but why do only the headlights come on. What happened to being more visible from the back?

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

rickjordan,

Good question. I took my rear lenses apart to clean them the other day. I noticed that the two inner most red areas have a hole for a light socket but were empty. Having lived in Germany for 12 years I know that theses are used as rear fog lights in europe. I am assuming that for whatever reason the US models were not equipped with them. My thought was to run a wire back to them and install sockets and bulbs then hook them up as rear DRL.

I am still only comtemplating but I think I will eventually do it.

Clancy, My VW Passat is the same way. Actually there is a company that sells the European light switch to be installed inplace of the USA light switch. The Euro. one has a position for turning on the rear fog lights and alot of people wire this switch in and install bulbs in the rear sockets. My neighbor has a 1991 Audi 100 that has a functioning rear fog light, but only on the driver's side. There is a switch on his dash specifically for this rear fog light. The only reason I can think of on why they don't send the cars over with the rear fogs would be it would reaaly confuse people. There doesn't seem to be any rhyme or reason on why some Euro. cars have and others don't. My W116 has the feature of turning on either the left or right parking lights when the car is off. I know that this is for parking on the street and making your car visible. Now this feature I know confuses people. The other night, when I turned off the lights I accidentaly went one positon too far. Somebody got my attention and told me my lights were on but only on one side. When I told them that it was normal, they went "huh".

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

I know what you mean, my model has the same "Parking Light" feature as yours. When my wife first drove it she asked what it was for and I explained that in Germay there are a lot of unlighted streets in the country and this feature was used to show the car to passing vehicles at night so they didn't clip them. Her resonse was also "huh"....LOL

I know Subarus have daytime running lights front and back. They're the only one I can think of with this feature. The interesting thing there is you do have the choice to switch them off. The lights work on the ignition switch so if you leave your light switch on, your lights come on when you start the car. You can turn them out if you so desire but you never get stuck because you left your lights on in the parking lot at Walmart. I'm sure there must be an override so you can turn on the lights without the car running but as I don't own one, I'll never be able to fill you in. Here, in Canada, it has been law since about '86 or '87 that every new car sold be equipped with DRL's. Cars without them are becoming more and more scarce. Just a few of us with old Mercedes and Volvos...