Old School Wiring Gurus Please Step Inside (headlights)
I got a set of LED headlights to replace the old halogen bulbs in my '84 Allegro. They got great reviews, though some users said they had to swap the low and high beam wires. It's a standard 4 light system with 4x6 bulbs. Or so it would seem. I couldn't get the new lights to work properly on the low beam setting. The low beam bulbs will only come on with the high beams. And when they do, they come on as high beams. If I switch the wire on the new bulb, I can get the low beam setting to come on (just one row of LEDs light up). But under no circumstances to the bulbs light up when I switch to low beams.
It would seem to be a simple fix - just swap the wires. But it isn't. I can't figure out how they have this thing wired up. It should be simple. 3 prongs on the low beam bulb:
Ground (black wire)
High beam + (red wire)
Low beam+ (yellow wire)
The high beam is 2 prongs, presumably ground and hot.
When I pulled the wiring out, I did not see what I expected. The red and yellow are spliced to the high beam plug. I had expected to see the red and black running there. In testing the low beam plug, it seems like the polarity is reversed on the low beam terminal. With the high beams activated, I get +12V on when I test from the red to the black and a -12V when I test yellow to black. That would allow the normal headlight to work, but not the LEDs.
Just for fun, I plugged them into my '64 Impala's 4-light system. They work beautifully and without having to swap wires around. So there's something goofy in the motorhome wiring. The lights have always been really dim, even for old halogens. Not sure if that's related.
It would seem to be a simple fix - just swap the wires. But it isn't. I can't figure out how they have this thing wired up. It should be simple. 3 prongs on the low beam bulb:
Ground (black wire)
High beam + (red wire)
Low beam+ (yellow wire)
The high beam is 2 prongs, presumably ground and hot.
When I pulled the wiring out, I did not see what I expected. The red and yellow are spliced to the high beam plug. I had expected to see the red and black running there. In testing the low beam plug, it seems like the polarity is reversed on the low beam terminal. With the high beams activated, I get +12V on when I test from the red to the black and a -12V when I test yellow to black. That would allow the normal headlight to work, but not the LEDs.
Just for fun, I plugged them into my '64 Impala's 4-light system. They work beautifully and without having to swap wires around. So there's something goofy in the motorhome wiring. The lights have always been really dim, even for old halogens. Not sure if that's related.
