The Stovebolt Site Forums The Shop Area The Electrical Bay high beam indicator light

turn headlights on, indicator light comes on bright, when I switch to high beam, indicator light is dull

funky wiring someplace, time to get out the wiring diagram and multimeter

Bill

Bills right. The high beam indicator tends to be "dull" during low beam operations because instrument panel light from the other bulbs bleeds over into the light socket.

Somehow either your indicator light or the headlight wiring got switched around.

Or current is passing through the hi-beam indicator looking for a ground. If the juice can't find a ground at the headlight it travels through the other filament in the bulb and back up that wire. The grounded hi-beam indicator is one place it can find a ground. The headlight on the other fender is another. The tail lights are another place.

You need to check your grounds and add some if necessary.

Original or new wiring? What kind of vehicle?

Should be one wire going into the socket for the high beam indicator light. This means the grounding has to happen where the metal socket contacts the metal instrument cluster housing.

So it can't "hunt" a ground from any where else. It has to ground there or it won't light. Since it's bright then it's getting a good ground. Why it's bright on low beam and dull on high is another story. So it's important about whether we have new wiring, or old.

Might make sure the mounting points for the gauges are clean so that the gauge pod is well grounded.

What year model?

Cletis is dead on IMHO. A bad ground can do some funky things and really make you scratch your head.

Your beam indicator lamp is on the wrong terminal.
Trace it back and move it to the upper beam terminal.


Good luck

I said nothing about the indicator light not being grounded. I said, in other words, if one headlight is not getting a good ground, power to the low beams will travel through the high beam filament, back up the wires, light the indicator as it grounds there.

Checking the grounds certainly may fix it. Won't hurt it.

My experience has been that when a bulb has poor grounding, then the bulb is dim as well as the indicator because of the amount of resistance in the circuits.

Sounds more like he has some bare wires touching that shouldn't.

But I've been wrong before. Will be again.

ding ding ding, we have a winner

Bill

it is a 48 gmc 1/2 ton, it is all new wire, all new switches,the only thing I have hooked up is the headlights, parking lights, brakes lights and directional...my ground in coming off the engine then into cab, at a junction box, then separate ground wires to front and back, all lights front and back work great, I have no lights for the gauges, only wire hook under dash is the high beam indicator, from dimmer switch, have high beam wire to headlights, same with low beam, high beam indicator wire hook to high beam bulb, maybe bad dimmer switch, also tried hooking wire from high beam connection to high beam indicator on dash, still bulb works same way.

Is the high beam indicator grounded? Your ground system seems quite complicated, and most electrical problems are caused by bad grounds. How big are the ground wires too? I'm using 4 gauge cables for ground from battery to block, block to frame, and cab to frame.

Using stock under the floor dimmer switch?

my high beam light is with my speedometer, should I try grounding the speedometer unit?

if the beam indicator didn't have a ground it wouldn't light - what folks are saying about ground problems is there may be some other light that isn't getting a good ground so it's using the path thru the indicator light to ground ..... unlikely, but possible

Bill

will keep looking, thanks for info guys...

If it's like a '54 the headlight ground attaches to the inner fender. Clamp a jumper cable to the inner fender and the negative terminal of the battery and see if it makes any difference.

If all the lights are bright, then the grounding for them is good. A poor ground to a light leaves that light dim compared to the others. A headlight with a poor ground will look orange in color due to having to hunt a ground.

So if they are all bright (high beam as well as low beam) and your tail lights are bright then I would have to lean towards the indicator being wired to the wrong terminal on the dimmer switch.

Is this a stock under the floor dimmer switch, or a later dimmer mounted inside the cab?

this a brand new dimmer switch that is mounted inside the cab, all wires are labeled what they are, and all lights are bright , high beam, low beam, brake lights and tail lights...

Used the upper connection for the power going in, and the two lower connections for the lights? If it has the typical two post on the side closest to the floor and then one above them.

Possibly a bad dimmer switch. Sounds like it's wired correctly with all that working.