Hello,
I thought I'd like to share my experience. I've run into somewhat similar problem as Thoughtful_One. I have a '92 Nissan 240 SX.
Everything's great until one day my right Low Beam started not functioning. My left side Low/High beam however were both working. My right side High Beam was working, just not the low beam.
So I went to an exhaustive list of testing:
1. Check the fuse2. Bought a new seal unit for the headlamp3. Put Left side headlamp (working one) to the right4. Check voltages on both left and right sides (I get 12 V out of low beam and high beam when I flip the switch from the driver seat, even the reading from my right side gave me 12V. This puzzeled me as there CLEARLY was voltage going to the right side, yet low beam didn't come on!! )
None of the above solved my problem. And performing step(4) above led me to believe maybe somehow my wiring wasn't supplying enough "current" to the right side for Low beam operation? I was confused, until I read vancouverbc's very useful and nice pictures of the relay and wiring diagrams at
zerothread?id=244906
I took his advice to check the relay ( I didn't do before! ), swapping Retraction Relay 1 with Retraction Relay 2, since Retraction Relay 2 is connected to the right headlight. And guess what, it worked.
It wasn't that I had a melted relay, I think somehow Retraction Relay 2 connection with the relay box was loose, and as soon as I took it out and put it back, IT WORKED!!
I still don't understand why if the Relay wasn't properly connected, how I got 12V out of my measurement. However, the moral of the story is that often it's the little things that are causing the headache. If you have similar problem, make sure you CHECK FUSE AND RELAYS FIRST!!
Jeff