General 12 volt knowledge is eluding me these last few days.

I am having trouble with my headlights. One half-works, one works. Here's the story:

Had passenger bulb out. Bought some new ones.
Replaced both bulbs.
Move switch to "low", both bulbs come on very slowly and dim.
Check battery, 250 CCA and 12.54V when off. Turns over great. Battery good.
Move switch to "high" drivers side goes to full brightness, passenger side goes out.
I switched the feed harnesses, crossed them over so they would operate the opposite bulb.
Same,drives side bulb low and high work, dimly and brightly, respectively. Passenger side, dim on low, nothing on high.

When both lights are on in "low" beam mode, If I disconnect the drivers side harness, the passenger side light goes out.

I have physically switched the bulbs around also and the testing yields the same results.
Results are the same with the engine running or off..

I believe (somehow) that the lights are in series. Some wires in the harness from drivers light to pass light are looped back.. It seems like there is not enough voltage or something to make the lows activate fully, and only enough voltage to run the first bright light in series.... Harness seems intact, nothing that I can see visually doing a cursory check... Is the switch my next stop?

Can a 12 volt guru take a stab at this? I'm not getting 12v on the high beam pin on the passenger side... with the harnesses crossed over this is also the case... dirty contact in the switch somehow??

Just weird.
Thanks in advance for your consideration,
Pete

 

OK, I think I'm on to something, still need help though.

When the low beam switch is on, the passenger light bulb has BOTH filaments energized, with no voltage on the "bright" wire. The drivers side has only one, however dim.
When high beam is on, passenger light is off, drivers side light works properly.

 

I think I found it.

 

Yes, looks like the switch was shorting. Though I was thinking bad earth when I read you post, as one broken earth wire can give all sorts of strange effects too.

 

yeah after a good cleanup, that DIDN'T )(@!&&%$ FIX IT. Now it's being even weirder. Ill post more test results after I get the 12v power supply moved over to it and gather some data...