Wonky headlight..., back again (post 17) Options

[Spoke]

Low beams are only getting 6 volts at the bulb.

Goal here is to find where the other 6V is being dropped. Measure each bulb terminal to chassis ground. It could be a couple of things:

1) WRT chassis ground: one terminal is at 0V, the other at 6V: Most likely your switch, fuse, or wiring to each. Do the same voltage tests at the fuse (fuse to chassis). Fuse voltage on each side should be identical (no voltage across the fuse). Measure fuse voltages on the wire spade, not the fuse itself.

2) WRT chassis ground: one terminal is at 6V, the other at 12V: Ground issue to the bulb. Trace the ground wires and correct bad connection issue.

3) WRT chassis ground: one terminal is at 3V, the other at 9V: Combination of both ground and switch/fuse/wiring to each.

[VaccaRabite]

One test that I am going to do this evening, which should determin if the issue is upstream or downstream of the fuse box:

Unhook the upstream yellow wire that powers fuse 3&4 (low beam headlights) from the fuse panel. that should isolate the circuit from any of the relays or switches.

Put a test wire from battery + to input fuse 3.

The lights should turn on, as I am taking all the switches and relays out of the circuit. If I get full power, I know the issue is up stream of the fuse panel. If I get dim lights, I know the issue is at the fuse panel or down stream.

Any errors with this logic?

I should note that the lights are open right now with the motor relays removed so that they stay that way. Test would not work so well if I was lighting up the inside of the light housing.

Zach

[VaccaRabite]

Just finished my wire test.
Everything from the fuse panel downstream to the lights is golden. Full voltage.

So.

That leaves the headlight switch or a bare wire under the dash. I am going to go take the lower dashpad off so I can check it out. I'm guessing, though, that my switch is shot - and I don't have a spare one on hand right now.

Zach

[Dr Evil]

I may have a spare. I know where I can get one, and I think you can use the bus one as the terminals are the same. There are options.

[Spoke]

Disconnect NEG from Battery and pull out your switch. With the switch and the fuse panel safely not touching anything, find the TO and FROM wires for the lights, turn on the lights and measure voltages at these wires to chassis.

This should help isolate the switch as the culprit.

[VaccaRabite]

I'm back inside for the night, and I made progress.

I got my fogs/driving lights back up. Which means I will be able to see at night.

Once I pulled the lower dash pad out, and pulled the light switch down under the dash for examination, I started getting 10 volts at the low beams. Thats improvement. But they still take a second to build power - its not the instant on like the high beams have. Its almost like the low beams need a relay to switch in high volume current.

Now that I am sitting here typing it out, I did not look to see if the lights were instant on when I ran the test wire, but I believe that they were.

Anyway, I looked up at the under-dash wires and could not find a cut wire that might have been rubbing against the chassis. I am more and more convinced that it is the switch. Tomorrow I am going to button up the front end and get everything aimed. I am also going to run Spokes test and measure voltage at the switch. I was going to do that tonight, but I got tired. At the fuse box input, I have full voltage.

Zach

[Spoke]

I wouldn't expect a rubbed wire or anything like that. If a wire were rubbing against anything you would have let the smoke out and it would have made a real mess and stink.

What I think you have is 30 year old oxidation on all the connectors. When you look at the connectors, there is a very very little bit of the connector actually touching the spade.

All around that small area of contact is exposed metal which oxidizes immediately and it builds over time. Just a little vibration and the vibration may be caused by heating and contraction, and the metal contact is now rubbing on an oxidized part of the lug and you get a bad connection and voltage drop.

Sometimes jiggling the wire (this is an official electrical secret) will improve the contact and your lights will get brighter. This is a hint as to your voltage loss.

You switch *may* be ok, just the spades and connectors are oxidized and need cleaned off with 400 to 1000 grit wet-or-dry sandpaper; dry of course. Contact cleaner sprayed after the sanding will remove the residue but it won't by itself, remove the oxidation. Your spades should look nice and shiny.

Also clean the edges of the connectors. I do this with a real little file. Sometimes I tighten the connectors by crimping (just slightly) the rolled parts of the connector.

Just this weekend I fixed the electric passenger window on my 911. The window would go down but not up unless the button was pressed time and time again, and even then it didn't go up fast. The culprit was; you guessed it; oxidized lugs. Cleaned the lugs with 400 grit W-or-D sandpaper and crimped the connectors and the window works like a charm. The oxidation on the connectors on my 911 is only 24 years old.

[VaccaRabite]

I'll clean them tonight and report back.
I am also going to do the wire mod on the headlight switch which will allow me to use my driving lights with the parking lights, so i don't need to raise the headlights to turn on the driving lights.

Those Pilots put out a lot more light then my headlights. I LOVE them.

Zach