Originally Posted by Renntag

Scott,

Great right up. Thanks for the extra bit of info on the N7. I have lamp warning lights on from time to time and I have no lights out. I have dim headlights and have cleaned the grounds and chased wires. While my lights are still dim, I drive on High beam at night, clearly i have not resolved this issue. As a last resort, I did think of doing just what you have described.
Now that I am trying to install some Euro lamps I think I may perform this relay mod.

I would still like to get wiring diagrams for the lighting system on an '87 300TD.

Thanks in advance to anyone that can help.

Originally Posted by scottmcphee

I said I'd post a few pix of how to do quick surgery on your N7 bulb out indicator module. Turns out it takes a double frontal lobotomy to make N7 not pay attention to the headlights on the car. One nick for the low beams, the second nick for the high beams. I'll leave it to you to figure out which is which.

You can do this mod if for any reason you are getting dash lamp out indicator for headlights or highbeams, and they seem to be working fine for you. Maybe you can't figure out why, or simply don't want to figure out why, and it's just annoying because things are working just fine. Maybe your bulb wattage is off, or you upgraded to HIDs, or LED lights, or whatever... I did it because my "lamps" had been converted to relays, as noted in above post.

Here's how to do it.

Find and remove N7 module from the car, it's in the fuse box. Take it out and open it up.

Note the WHITE arrows I painted on the photo pointing to the plastic peg(s) that prevent wrong insertion. This will orient yourself as to which side of the unit you should be working on.

The PURPLE circles show what to cut on one circuit board.
You can cut that thin trace leaving both the encircled pads. Or you can do what I did, heat and lift those two diode leads from the board. Just left them hanging in air a bit off the board. (This way I can re-insert the leads in the future if I ever want to revert.)

Flip the unit over. Note again the WHITE arrows to re-orient yourself to correct side of the unit.

The BLUE circles show what is cut on the other board. Cut either that trace going between the two encircled pads, or lift the jumper wire out at one end.

Now pop it back together, and re-insert into the car.

Doing this mod leaves all other bulb indicator warnings intact.

Originally Posted by arcticathlon

could you show me where the headlight pins are? that way i could try and trace them. and how much would a modded N7 cost?

Thanks

Originally Posted by Dr_SJH

I wish to entirely remove the low/high beam headlights from this circuit. Apparently I can remove 4 diodes as per this link -

http://www.peachparts.com/shopforum/showpost.php?p=2504982&postcount=12

Or entirely bypass the relay as per this post -

http://www.peachparts.com/shopforum/showpost.php?p=2587059&postcount=3

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I'd like a little advice as to which leads I should remove from the relay and tie together.

Thanks.

Originally Posted by k26ripley

Thank you scottmcphee and 300d91 for your awesome pictures and details. I added HID when i replaced my headlights (buckets and all). Though they were supposed to be error free etc i threw a exterior bulb warning. My N7 was the variety 300d91 showed the fix for. I can say that with some careful snipping, the warning bulb is off! You will need the smallest snips you can get to perform the work but all told it was a fifteen minute job. Thank you again for the super easy fix!

Originally Posted by scottmcphee

3. upgrade voltage to the headlamp. This is what this original poster was asking about 3 years ago. There is too much voltage drop through the MB + side of the supply to bulb, more on that later. Here's how to minimize it: bring both plus and ground from the battery posts to the lamp area on minimum 14 AWG wires, 12 AWG is better, these beefy new wires must be fused at the battery side. I used 20AMP per wire for a good reason. Pro-tip: avoid having to run 4 wires by running a common rail of 2 wires that passes behind by each headlight. Rotate the second side of the car's connections to the rails so it's high beam shares the low beam rail of the other side of the car. Both wires are active for low, and and high - just the roles reverse. When you do this, one blown fuse means one side of the car remains working on low beam and the other side of the car on high beam - but you'll still have some light at all times. If you notice this failure pattern it's probably your fuse and not two filaments in different bulbs going at the same time. Beware, it is possible to hold the light stalk just so (as if doing flash to pass in slow motion) to get ALL FOUR beams ON at the same time. This is why I chose 20AMP fuses for the 2 wire idea. If you're antsy run 4 wires. Back to the program... cut the three wires going to each headlight lamp (3 wires for 9004 bulb), leaving enough length on the socket wires to remain useful. Repeat this for each side of the car: wire the car-side of the bulb supply with 2 relays, one relay coil for low beam, other relay coil for high beam, using car-side bulb ground for the relays only. Now when you operate headlights you'll only get relays clicks and no light until you connect your beefy + supply from the battery through the relay contacts to the bulb socket. One rail and a relay for low beam, the other rail and relay for high. Attach the bulb socket ground to your beefy ground wire. You can't get lower voltage drop than this for any headlight style assembly or bulb type!