Guy

Hello,

My right side low beam doesn't work. High beams work fine on both sides. Fuse 27 has been replaced and i have continuity from fuse 27 to the terminal at the headlight. Ground on right side has continuity to chassis.

Any suggestions on what to check next?

BEFORE:

Alan

Have you checked the bulb itself with a continuity tester?



Alan

Guy

Thanks, Alan. I should have mentioned that the old bulb had the same problem. Bulbs are good and have been tested. I can also jump 12v directly to the bulb and the beam will illuminate. I was under the impression that the top post (yellow) is the high and the side post (white) is the low beam. This doesn't jive with the above diagram, however.

Alan

Check the wiring side to side, the diagram is correct.

Also check the voltage at the bulb pin when active and the bulb is connected

Alan

Mrmerlin

I would suggest that your break in the wires is at the metal crimp just under the headlamp,

where the harness is captured by the metal loom holder,

its quite common for the wire to break due to it being pulled too tight.

when refitting, check that the wire has play with lamps up and down

The Forgotten On

I had the same thing happen to me with the headlights in my 81. The relay went bad so I replaced it with one out of a parts car and it was all well again.

The issue with the wiring getting worn through is rather common so it wouldn't hurt to check.

Alan

You didn't have this issue.. the relay drives both sides lighting from a single source - if one side works the relay is OK

Alan

The Forgotten On

Alan, I know this sounds weird but that is what happened to me, the relay was not working correctly.

Another thing to check is to see if the ceramic back plates have corrosion on the metal contacts. This also failed me when I converted to H4's. I do not know if yours are used or not so it is worth a shot to check the continuity of the plate.

Guy

Thanks to all. Call me an idiot but my initial continuity test was done with the bulb plugged in!! With it disconnected, I lacked continuity from fuse 27 to the YELLOW terminal.

Sooooooo........

I checked the wiring right where the metal crimp tag was and found a very small break in the insulator which allowed water to enter and corrode the wire badly. I replaced the section, soldered the ends and heat shrunk the whole shooting match.

You guys all rock, as usual!! Thanks so much!!

Mrmerlin

Keep Em Flyin!

Alan

If the relay was not working neither side would have worked properly.

So the relay simply cannot be the cause for just one side not working right, if it was just one side and it worked after changing the relay - you actually did something else during the process that really fixed it...

I correct these things for diagnostic benefit, folks just want to know the few things that can quickly identify & fix the problem, chasing after things that cannot possibly be a cause can be a great waste of time and possibly also a lot of money.

This is not just for this instance - but for other folks with similar issues reading this later in the archives...

Alan

soontobered84

Thank you Alan

I am a virtual electrical idiot. Your posts generally help me immensely, although when they get way too deep for me, I call in reinforcements with greater electrical knowledge (so I don't screw it up).

Mrmerlin

or let the smoke out^^^