Headlight issues

[e3027]

I am having an issue with my car. Neither of the low beam headlights will turn on when the headlight switch is pulled. When the switch is pulled the corner lights and tail lights do turn on. They will turn on when the high beams are turned on using the stalk on the steering column. I have followed the directions in the bentley service manual for debugging this issue. I have gotten the correct signals at the relay box and I have tried using a different relay. I am suspecting the issue is with the switch but the bentley manual is only for the 88 and up switches not the 1984 to 1987 switches. Can anyone provide me with any explanation on how to check this switch?

Thank you

[tomstin]

Taking a look at the wiring diagram for my 85. It appears there is a low beam relay (K4), then a low beam check relay (power distribution block). I always like to start simple, have you check for power at the back of the low beam itself? It is a dual filament bulb so there is an opportunity for both low beam filaments to be out. Are you getting a warning light on the check panel?

[7pilot]

Replace your low beam headlights. I had this exact scenario on my 91 M3 and went on a wild goose chase after a replacement head light switch relays and high beam switch. Had spares. Changed relays... nothing.After some thought, I replaced on low beam...start easy yeah? Found That I now had the one low beam working. So...

[7pilot]

If the dual low beam replacement works for you, put a volt meter on the battery and make sure that the alternator is behaving itself and not overcharging the battery and the electrical system....this was the ultimate cause of my dual low beam failure.