Hi everyone. I want to add driving lights to my 1989 240 DL. Where I live the driving lights must turn off when the high beams are off.

My plan was to run power from the high beam circuit through a rocker switch to energize a relay which pulls power from the battery for the headlights. I thought the cleanest install would be to pull the rocker switch power from the turn signal/headlight switch, so there would only be a single wire running from the rocker switch through the firewall. I checked the wiring schematics I had, but couldn't find a colour code to indicate which line to tap.

I thought I would just probe the wires coming off the switch, thinking that one wire would energize when the high beam cirucuit is on. That doesn't appear to be the case. None of the wires change state (hot to cold or cold to hot) when testing, so I'm a bit confused. Using the basic test probe.

I have four wires connected by spade terminals to the turn signal switch. They are Green, Blue, Brown and a double Yellow. All the wires except the yellow are either hot or cold and don't change state. If I probe the yellow, a repeating click occurs, almost like an emergency flasher relay.

I'm thinking of something like the Hella-500 series lights. So my questions..

1) Which wire do I tap to energize the rocker switch?

2) Better/Easier to tap at the turn signal switch or somewhere else?

3) In-line fuse between the tap point and the rocker switch? If so what size? I was thinking 10amp.

4) What size relay? At 12v, 55watt, I calculate about a 5amp draw/light. So would a 15w relay be appropriate?

5) What size feed wire for the lights? Battery to relay, then relay to lights. I was thinking #10 Battery to relay, a spliced #12 to each light. Overkill?

6) I was planning on mounting the lights slightly off the center on the bumper top. Does anyone have any experience on how this mounting might impact cooling/airflow for the radiator. I know theoretically it will impede cooling, but does anyone have any practical experience - like mount the lights as close to the headlights as possible. Upper Mid-Altantic here, so cooling demands aren't like the South-West.

7) Any mounting solutions other than drilling holes in the bumper?

I put a new dash in the 240, so its all torn apart, just waiting for the new wiring to be added. Thought I'd ask everything I could think of before installing and learning the hard way!

Thanks!

 

Did you ever make headway on this issue?

 

Unfortunately I didn't. I know there has to be a way to trigger a relay from inside the cabin, but I can't find it. I think I'm stick running a wire from the headlight relay on the fender back inside the cabin to the switch, then back out to the relay under the hood. Do-able, but not a very clean install.