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Tips
Tips

no low beam head lights

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tomgt6

Jedi Warrior
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I need some help.

I am working on getting a 73 GT6 back on the road but I can't seem to get low beam head lights to come on.

Here is what I have done.

I get lights at high beam. Should I also get power to low beam lights at high beam?

I tested the bulbs and the lights work for both high and low beam.

I then tested power at the socket for low beam and the power was like 2 volts. I then went inside the nose and pulled the power to the low beam power and was getting 12v at the power in the nose. I put on new connectors in the nose and now I get 12v at the socket. Still when I turn on the lights no light.

I then tested to see if I was able to close the loop (tune is what I call it because you get a tone if the loop is closed) and I get good tone and the meter goes to .02 or so.

Turn on low beam and still no light.

I take a wire right from the power in the nose and get 12v and attach it to the bulb and also attach a ground from the bulb to a different grounding point in the car and still no lights.

I go to the switch in the steering column and test the volts again at the switch and get 12 volts when I turn on the light switch and move the high and low beam switch on the column. I still get light on high but on one low beam.


So the only thing I can think of is the low beam power is grounding at some point along the way. If there is no load with the bulb I get the 12v but once the bulb is attached it takes the easiest way to ground.

Help. I not sure what else to test.

The one item I didn't play with was the light switch, maybe some wires are touching there but my son tells me everything looked ok there.

It has to be grounding out, what do you guys think.
 
Not grounding out ... what you have is a high resistance somewhere. With the bulb disconnected, you see 12v all along the circuit, because there is no current flowing to drop the voltage over the resistance.

Go back and repeat your voltage checks with the low beam headlights still connected. You'll quickly find the bad spot (which I am guessing is the high/low beam switch, but could be anywhere between there and the bulbs).

If it was grounding out, you would see the smoke leaking.
 
Andrew Mace said:
But speaking of grounds, I would double-check the ground connections from the headlamp subharness to the main harness.
Click to expand...
Can't hurt to check, but since high and low beam share a ground, it's not likely to be the problem.
 
:iagree:

This is ~usually~ the 'dip-switch'. Poor contact on one side or the other.

A "qiuck-n-dirty" pseudo-fix would be to shoot some CRC 5-56 or 2-26 into the bowels of the switch and work it high/low repeatedly to see if it improves. The proper fix is either disassemble the switch and physically clean the contacts or replace it.
 
I agree it's probably the dip switch. Try slowly moving the lever up and down while the lights are on. My 75 only has low beams when the lever is first brought all the way down and then raised ever so slightly. At that point they stay on.
 
your best fix would be put relays on your high and low(dip) beams and take the High current off your switches, I assume you dont have relays on your lights,

Hondo
 
I put relays in, however the switch is still faulty. Since it is daylight savings time and it doesn't get dark until I am in bed, for me it's not a problem.
 
OK, you guys were right. The contacts in the switch were dirty as can be. Good job everyone.

Now lets see you can answer the next question I will post.
 
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