belair

I searched a previous thread on this topic and it seemed to detail methods for post 87 and early models . Ideas on an 86.5?
Thanks

dcrasta

Ahhh.. You too ? Mine is making my side markers not workie (I think..)
1 side marker is on (left rear) the other 3 work when they feel like it.

WICruiser

I ssem to recall a bypass plug you can make to replace the bulb control unit, but I am not sure where I saw the wiring diagram. I will try to do some digging this weekend.

robot808

Porken came up with one, not sure what model years it is good for. The Mercedes plug he used has proven difficult to come by. Ask me how I know.

EDIT: My comments were in reference to the lightbulb warning feature. Sorry for any confusion.

The reason I haven't fixed it properly is because all of my lights actually work, the wiring was just kind of rigged so the warning light goes on. One day I will actually fix it...

rexpontius

why not fix all bulbs and have a working light control :-)

I did it on my 86.5 and replaced all bulbs.

Most difficult one, was the side marker right-rear, where the gas-tank is a bit in the way.

76FJ55

I had issues with my right rear parking lights not working on my 85. I initially thought is was the bulb control unit, so I removed it and opened it up. It is a very simple unit and could easily be bypassed if you had a similar shaped plug to make a jumper circuit out of. I determined it wasn't actually the control box and determined it was actually the connector where the bulb control plugged in. I cleaned this connection and have not had a problem with getting the lights to work since; however, the bulb warning still illuminates on the dash even though all the lights work. basically the control unit is two counter wound electromagnets (one for the left and one for the right) with a reed switch mounted in the middle. provided the current flow is the same in each leg the magnetic flux from each coil is balanced and therefore cancels and the reed switch does not close. but if the current flow is uneven the magnetic pull of the higher current flow will cause the reed switch to close illuminating the bulb warning. I haven't had a chance to experiment with it yet but I was thinking since the right and left parking lights are on separate fuses it should be fairly easy to check the current draw on each circuit and then increase or decrease the wattage of the bulbs to balance the current in each circuit. Whenever I get a chance to play with it I'll let you know how it turns out, but is is rather low on the priorities at the moment so I can't say when that might be.

belair

I have replaced the bulbs with correct wattage in pairs, cleaned contacts, dielectric grease, etc. They all work but the stop lamp warning light is on most of the time even when I haven't even hit the brakes yet. Then it sets of the very bright "!" and the reset button. Sometimes it will turn off the "!" sometimes not. Maddening.
Previous threads mentioned pulling a couple of pins in the module, but which ones on a 86.5.