Some time in 2004 I made a post with the above title, but I can't find it now— using the new SEARCH feature. I remember when Ken C saw it he thought I'd plagiarized his 1987 "Rolling" article (see this thread). I may have read Ken's article, then subconsciously recalled the concept some 6 years later when I did my first 240 DRLs in 1993. But I tend to believe that it was more of a coincidence, based on our independently discovering the unused bulb filaments identified as "Day Running Lights" in the earlier 240 wiring diagrams.

At any rate, in the thread linked above, Dave Shannon said a repost of my DRL version might be worthwhile, so here goes...

The accent is on "Fairly" easy. After Step one, it really is easy. I've done it on '76 up thru '86 240s. And it should be possible on any car with the 2-filament bulb in the upper front Parking Light. On USA cars, only the 4cp/5W Parking Light filament is used. The unused 32cp/21W filament (same as Signal Lights) is used for DRLs in Europe. This brighter filament can be wired to light when running, and go off when Park or Headlights are turned on. The Amber light makes your car noticeable (without being obnoxious or annoying) to oncoming cars—and to cars approaching from either side (something Headlight DRLs fail to do).

1) (the trickiest part*) Adapt & install a wired bulb contact** to match up with the unused 32cp lug on the bulb. Do this on each parking light.

2) Run the new Right side DRL wire to join with the Left one, and then to a single common wire that will be connected from the Normally Closed terminal of a "new" relay (usually terminal #87a on Bosch relays). I put the relay inside, above the driver's knees. Run this common wire along the left side and thru the firewall for access to the relay.

3) Next, run a wire to the relay's Operating/Input terminal (#30) from a "Key On II" fuse box terminal. On the '86 I used #5, Rear Window Demister (for +12 volts only with Key ON).

With the relay deenergized, the 32cp DRL filaments will now light with Key ON. We need a way to turn them OFF when the regular lights are on (Step 4).

4) To energize the relay (turn DRLs OFF), wire the relay's "pick" terminal (#86) from Fuse 15 or 16 (+12 volts to Parking Lights). (You may need a "piggy-back" terminal extender here, if all the available terminals are in use.) Then wire the relay ground terminal (#85) to any convenient ground point.
Now, when the Parking light fuses get powered, so does the relay. The DRLs then go out, and the Parking Lights come on via the normal wiring.

*I'll admit that getting the bulb socket adapted is not a slam dunk. Some early cars already have the hole drilled in the right place. Others have it marked but not drilled. Others require some careful eye-balling and marking of the bulb, so you'll know where to drill for the new wire. (Those that only take the small, single-filament bulb won't work for this project.)

**For the "new" wire and bulb contact, I've scrounged from junkers and also used wiring accessory parts from Pep Boys. Most all places like that have wiring ends that will work. You can buy a Radio Shack relay or use one from the "yard". Just make sure it has a Normally Closed terminal for powering the DRLs.

If you endorse "reasonable" DRLs as I do, I think you'll be pleased with this project. I did the '86 in November 1995 and the relay is still there. So relay life is not a concern. The bulbs last forever too.



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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.