Chrysler Repair: 87 head lamps: low beams dont work, highs do, headlamp switch, low beams

Question
when i turn on my low beams nothing happens but when i turn  on my  high beams all four lamps turn on and some time just the high beams turn on why is that happening ? i have  a 1987 Chrysler new Yorker

Answer
Hi Rich,
It is either the head lamp switch or the dimmer switch. You could
either remove the head lamp switch to check this out:
The power for the low beams is provided on the light green wire at the head lamp switch so you would see if 12V appears when you turn the headlamps "on".
OR You could go to the dimmer switch and verify that 12V is arriving at the dimmer on that light green wire when the headlamp switch is in the "on" position. If it is, then see if you get 12V on the violet trace wire of that dimmer switch when it is in the low beam position. If you have 12V coming into the switch but not going out then the contacts inside the switch are dirty or oxidized. You might be able to clean them with some spray circuit board cleaner.
That is the way to localize the problem. Because you are getting the high beams (sometimes along with the lows) you are definitely getting power into the headlamp switch, so that is not the issue. If you aren't getting 12V out of the headlamp switch on the light green wire then you could try the same cleaning technique there.
Roland