Tail light converter compatibility: '91 350SD
 

I am putting a trailer hitch on my 350SD, and am wondering about the compatibility of the trailer light converter (4 bulb to 2 bulb) with the "lamp defective" warning light system. Anyone have experience with this? I have heard of "powered" converters, but wonder if I need to spend the extra $ if a standard solid state converter will work without triggering the warning light.....Rich

With much searching, I did not find an answer yet, so I am just going to wire it up and see what happens. It seems that no one else has had the problem or asked how to fix it (from my search here and Tech Help). If the bulb warning light does come on, I will know exactly what the cause is. However, I would like to find a permanent solution eventually......Rich

You need to balance the load on 2 sides. That is how the bulb warning light monitoring relay works. The other thing you can try is to use LED lights. They draw much less current. Do you fab the tow hitch yourself? Would be interested to install it on my SDL.

Yes I fabricated the hitch, and am planning on making more for sale (eventually):
http://www.peachparts.com/shopforum/diesel-discussion/352321-126-trailer-hitch-fabrication-install.html

Helpful or not, here's 2 cents.

I have the un-powered converter in my '93 300D and it doesn't turn on the lamp out bulb. I don't believe I've had a trailer light out just yet to see if that triggers the fault.

My friend has the same year and model and we installed a powered converter in his. Mostly because his bulb out light was triggering at the time. Turned out to be poorly spliced wires for a headlight. Oh the gifts you find on a used car.

A hitch for a W126 you say? My brother needs one of those. It's a '91 350SD with a 3.0L already swapped in.

It could be that the sensor only sees fewer bulbs, and not more to turn the light on. I hope that is the case, but I will find out soon (just got back from A Z with converter in hand)......Rich

If it turns out you need a powered converter, I built my own using an unpowered converter and relays from work. All the original lighting circuit does is kick the relays, a miniscule draw. Easy and inexpensive to do.

As it turns out, I used my trailer on Friday morning and it worked just fine. It seems the circuitry senses less bulbs to activate the light, and does not care that there are more bulbs. I know the system is working because I now have a reverse light bulb out, and the warning light illuminates only while in reverse....Rich