Head light inop.

[raiderfan]

80' Liquifire is the sled. Sled came with a head light bulb with a contact broken off. New one works breifly and now nothing. Dimmer switch tests ok, wiring from dimmer to head light check out with the ohm meter, ground to head light checks ok. All other lights work. Tail, brake, dash.
How do I check the voltage to the head light? I may have gotten a bad bulb, but I would like to make sure before I buy another one.
I assume, I can check the bulb with a auto battery. Ground wire to each, and a hot wire should work high and low, right?

[JDT]

There are three contacts on a headlight bulb. One is a common (ground) that is used for both High and Low beams.
And one contact each for the H and L.

You can test a bulb these with an OHM meter or a car battery.

Just a note here... if the connector or wires going to the headlight have been repaired or shorted you can end up with power going to either the of the H or L terminals and no ground contact.
This will cause both H and L elements to get power but they are actually back-feeding through each other. The bulb will light but not very bright.

It is important to visually check the harness going to the headlight as there are many possible places for it to be damaged.
Some very common potential problem areas are insulation rubbed through from moving parts like jack shafts, clutch sheaves, steering linkage, ect.
Another area to check is when the harness goes under the bulkhead and the belly pan was dented up pinching the wires.

Heat can be another issue.
Look for sections of the wiring harness that may have been in contact with the muffler or exhaust manifold. This can cause the wires to short out in the harness.

If you unplug the head lamp and the dimmer switch there should be no contact between any of the three wires in the harness.

Another thing to keep in mind is a circuit may test OK with a meter but when you put power to it it does not work. Reason for this can be that the meter only requires a few milli amps to give a reading. But a headlamp requires a few amps of current. If there is a poor connection in the system it may not pass the high current required to actually light the lamp.

And finally and most importantly remember that sled lights are running on AC voltage not DC so have your meter set for AC when reading voltage.

[raiderfan]

All wiring looks good. I disconnected the harness from the headlight and the hi/low switch. There is continuity at the high and low wires. The ground is good. The "new" headlight is blown. The sled has heated grips which were not in the best shape, broken wires etc. I took all that off now.
Running the sled wire a meter hooked to the headlight wiring harness, I do not get the meter to read a constant number.

[xjfish]

It sounds like you could possibly have a faulty voltage regulator. What kind of readings do you see on your meter? You can temporarily load test the headlamp circuit with just about any old sealed beam headlight if you happen to have one laying around...

[raiderfan]

It sounds like you could possibly have a faulty voltage regulator. What kind of readings do you see on your meter? You can temporarily load test the headlamp circuit with just about any old sealed beam headlight if you happen to have one laying around...

I switch up to a needle meter in leu of the digital, with the old school meter I get a reading at the headlight connector of only 1 volt. High and low beam are the same just one volt. This is throttled up too.

Could the one volt blow the headlight, but be enough to light the rest of the lights?

[sledhead16]

Is your brown headlight plug melted that plugs into the bulb, that can cause a short and blow the bulb, you have a short somewhere in the headlight harness. If the other bulbs all work fine then your voltage regulator is fine and they ate all grounded ok.

[JDT]

Check voltage at the connector that goes to the dimmer switch and see what reading you have there.

You may have a bad dimmer switch.

[raiderfan]

Check voltage at the connector that goes to the dimmer switch and see what reading you have there.

You may have a bad dimmer switch.

Here's what I did, I unplugged the main wiring harness at the motor. Took a car battery, ground to body, positive to the yellow and brown wires in the main harness. All lights lite as they should, no headlight as it's blown. I have 12 volts at the headlight plug, high and low beams.
I ASSUME this has eliminated wiring issues. I hooked the harness back up and fired it up, checked the voltage at the wiring harness, yellow and brown wires in the connector, 2 volts max. Now this is before the voltage regulator so this is true output, correct?
Ok, soooooo, does this mean the lighting coil is NFG?

[JDT]

I think that you are reading DC on your meter.
When the engine is running it is AC that powers the lights.

One needs to be extra careful when using a car battery or any other 12 volt DC source for testing electric systems on a sled.
If you fail to unhook the engine connector and apply 12 volts to the main harness you will instantly burn up the lighting coil.
Also the same thing will happen to the voltage regulator if you do not unhook it before you hook up the external 12 volt source.

[raiderfan]

Ok, back at it. I needed a break. Power is good coming out of the main harness. BUT, when I checked the the power at the headlight socket the meter was all over the place. Rechecked rock solid. Re rechecked and meter is bouncing all over. Each time it was when I restarted the sled. I'm going to swap out the voltage regulator and see what happens.