1955 wiring problems

[55pickupman]

I have floor mounted dimmer switch. Trying to connect the Hi beam indicator light simple I know. But I get Low voltage from the terminal on the other side. High beam has high voltage while at the same time I get low voltage on the other side. I have a simple wiring system with no relays. Does anyone know how I can eliminate the bleed over or do I need to install a diode?

Also my buddy has the 2nd series 55 pickup when you apply the brake the left front parking light comes on. Cannot seems to locate where someone crossed a wire. any ideas on where to check would be helpful.

[dsraven]

check grounds in the bulb sockets and wiring at the trailer plug, if applicable. if one bulb has a poor or no ground at the pigtail or bulb socket then the power goes through the bulb element and the bulb body (where it would normally ground for either circuit) then, because it has a poor or no ground circuit, power feeds back through the other element sharing the same ground point and then exits in a way that is back feeding power (although less voltage due to the resistor effect of the bulb elements) through the other circuit of that bulb socket. in this case the low beam. you can easily check for a bad ground by simply turning on the lights and checking for one that is dim. that would indicate a poor ground in that socket or pigtail and the bulb is searching for a ground but can only find a circuit through another circuit. . if you find a light like that just check that socket for corrosion or pigtail eyelet ground point to ensure you have a good ground. I have often used a jumper wire from the pigtail ground wire to a known good ground point and if the bulb lights up like it should then the ground for that circuit needs attention. if the headlights are grounded to the rad support and the wiring there appears to be in excellent condition, like a good solid ground with a star washer under the eyelet terminal and no corrosion, then you may need to install a ground wire from the frame to the rad support because the rad support is relying on metal to metal contact with the rest of the body parts to complete a ground circuit. also, check to ensure you have a ground wire from the battery to the engine-like battery cable size, and one from the battery to the frame-like battery cable sized, and another from the battery to the body-like big enough to run everything in the accessory circuits-lights, stereo, airbag compressor etc etc.
make sense?
I have found that if you turn the lights on and a signal indicator comes on dim then there is a ground issue in one of the lighting circuits. start pulling bulbs till the turn indicator light goes off-bingo- found the socket that is the troublemaker.

[dsraven]

on the dimmer switch there should be 12v going to the switch when the lights get turned on and then 12v to one of the outlet terminals on the switch. the third outlet will have no power coming from it. then, when you switch the dimmer for the other circuit, it should have 12v to the other outlet terminal and none from the first outlet terminal. the voltage doesn't change for hi and lo beams, just the element in the headlight. hi and lo both get 12v it is the element that is different inside the bulb that makes hi brighter.
make sense?
keep us posted if you figure it out or not.

[Coupeguy2001]

I think you need a new dimmer switch if you get 12 volts to it, and voltage out of the other two terminals at the same time.
You are supposed to get 12 volts in to dimmer switch.....
Then you should get 12 volts out of only one of the other two terrminals.

pull off all 3 wires if they are not in a connector. If in a connector, crawl under and have someone turn on lights and push dimmer switch while you probe all three terrminals with a meter. One contact will have 12 volts all the time, and power will switch back and forth between the other two.

Then that switched voltage feeds the headlight.
the headlight has 3 terminals. one is ground, and one is low beam. the other terminal is high beam.
So say you turned on the headlight switch.
the light switch headlight wire goes to the dimmer switch. it's 12 volts.
You see that the low beam is on.
You push the dimmer switch.
the switch changes contacts internally, and sends the volts to the high beam terminal on the headlight.
there is a wire that goes from the high beam on the headlight up to the high beam indicator. when the high beam is not powered, the indicator is not powered either.
The low beam contact on the headlight has no volts with the dimmer in high beam..The low beam contact on the dimmer switch now has no volts.
Turn off the headlight switch, and the dimmer should stop receiving any volts

Check to see that someone did not switch the wires on the headlight plug. That would give you a high beam indicator with low beams.
If it's bad, replace it. They are less than $10. o reilly's can get the dimmer switches but you have to order it. It's less than $20