A few weeks ago i noticed none of my front headlamps works - dayrunners, lamps and highbeams dont work. All other electronics work, radio, back brake lights, turn signals, interior etc.
Fuses looked fine, and every now and again the dayrunners/headlamps would work - for a day or 2, then stop. Highbeams havent worked for weeks. I changed the fuses and same behavior.
Other than replacing the relay - what else can i look out for?
Thanks
The relay should fix it BUT… Find the grounds for the headlight harness and make sure the ground connection is not broken or badly corroded. I’d expect a ground on each side which is unlikely to cause BOTH sides to fail at once, but check anyway.
Cool thanks - i know next to nothing about cars, would you be able to link pics of the grounds on a headlight harness by any chance?
Maybe this will help. Knowing nothing about cars is one thing. If you are inexperienced at basic troubleshooting (methodically working through a problem), troubleshooting a wiring problem may be frustrating. In that case, you may want to enlist the help of a friend that knows how to trace wiring and use a multimeter or test probe to check continuity.
I don’t know where the grounds on a Corolla are, @q2klepto, but the wires are colored black and go from either one or both headlights to a screw embedded in metal. That completes the circuit back to the battery (-) post. The screw should be within a foot of the headlight but it might not be in a spot that is easy to see or get to.
Just unscrew the ground screw, the wire terminal and clean it and the metal it attaches to with sandpaper. Don’t grease or oil it, screw it back together and THEN dab a little Vaseline or grease just to keep it from rusting.
I agree with Mustangman that it’s unlikely that both grounds would fail at the same time, though it is possible. I would look for something that all these lights have in common. It could be the switch on the steering column or dashboard, a relay, or a wiring harness connector–maybe one near the battery got acid on it. The lightbub sockets can also cause this kind of probem, but would they all go bad together?
A wiring diagram would be most helpful, but you might need a little tutoring in how to read it. Basically, the lines in the diagram are the wires. find your non-functioning lights in the diagram, then follow the lines to wherever they go. If you come to fuses in the diagram, continue folowing the line past them: You already checked them. There might be something (relay?) that the lines from all the lights converge on. That is the item you want to check. The diagram should also show wiring harness connectors, which could cause your probem.
The symptoms are cassic indicators of bad / corroded / dirty connections or relay contacts. If the relay housing can be opened, the contacts can be cleaned using a sovent like MEK, or using emory paper. If the contacts are burned or pitted from electric arcs, you can try a fine file–like an old-school points file–, but they may be damaged beyond repair.