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Discussion Starter · #1 · (Edited)
:confused0024:Just got my '55 p/u on the road, including new wiring to the parking and tail lights. I was having a problem with the front parking lights and tail lights sucking a tiny amount of juice even when the old light switch was in the off position. I had a brand new Danchuk light switch for my '56 that is exactly the same that I hadn't put in yet, so I swapped out the "bad" switch for the new one. Repeat: It is exactly the same switch. So now the front parking lights are working correctly; hooray. But get this... the tail lights are now controlled by the dimmer knob on the light switch! When the switch is all the way in, the tail lights will go from off to bright by turning the knob. Both Danchuk and Eckler web sites show seperate wire pins feeding power to the parking and tail lights the same as the shop manual, so my wiring should not be the problem. Repeat: they identify the exact pin to use to control the tail lights. But when I pull the switch out to either the first or second position, the tail lights go to full power as they should. I removed the shaft and reinstalled it three times just to be sure, then I reversed the location of wires: tail lights into the parking light tab, and p-light wire into the t-light tab. Now the p-lights are dimmable when the switch is in the in (off) position and the t-lights work fine. Do I have a bad switch or a bad brain? When I get this problem solved (with your help) I have another minor question regarding the dome light; but that will come later. Cheers.
 

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i'll move it back to top for you. :anim_25:
 

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Trifive Automotive Electrical Wiring Expert
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:confused0024:Just got my '55 p/u on the road, including new wiring to the parking and tail lights. I was having a problem with the front parking lights and tail lights sucking a tiny amount of juice even when the old light switch was in the off position. I had a brand new Danchuk light switch for my '56 that is exactly the same that I hadn't put in yet, so I swapped out the "bad" switch for the new one. Repeat: It is exactly the same switch. So now the front parking lights are working correctly; hooray. But get this... the tail lights are now controlled by the dimmer knob on the light switch! When the switch is all the way in, the tail lights will go from off to bright by turning the knob. Both Danchuk and Eckler web sites show seperate wire pins feeding power to the parking and tail lights the same as the shop manual, so my wiring should not be the problem. Repeat: they identify the exact pin to use to control the tail lights. But when I pull the switch out to either the first or second position, the tail lights go to full power as they should. I removed the shaft and reinstalled it three times just to be sure, then I reversed the location of wires: tail lights into the parking light tab, and p-light wire into the t-light tab. Now the p-lights are dimmable when the switch is in the in (off) position and the t-lights work fine. Do I have a bad switch or a bad brain? When I get this problem solved (with your help) I have another minor question regarding the dome light; but that will come later. Cheers.
What is the dome light problem? It may be connected to this problem. Do the dash light work and dim with the knob? I think you have some wires in the wrong position on the switch. Maybe gray and orange or orange and black or violet. .... http://www.trifive.com/garage/56%20Chevy%20Assembly%20Manual/12-7.gif
 

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Discussion Starter · #5 · (Edited)
Thanks for diving into this with me. Here is tonight's info: I followed the wiring schematic and everything looks OK... 1) always hot red wire from ignition switch to light switch, then another hot red wire out to the fuse panel. 2) always hot gray wire from fuse panel to correct male tab on light switch, then from there, another hot gray wire to instrument panel lights. When I turn the rheostat the dash lights get dim or bright... BUT when the dash lights are dim, the tail lights are bright; when the dash lights are bright, the tail lights are off. Since the gray wire is always hot, all the above is when the knob is all the way in (off position). So... I disconnected the battery and got my VOM meter out. I turned my meter to continuity and sure enough, the meter shows continuity between the section of the light switch that controls the dash lights and the section of the light switch that feeds the tail lights. That means since the gray dash light wires are always hot, so is the section that the tail light wire is connected to. THIS SHOULD NOT BE! Why is the gray wire always hot??? I disconnected the hot gray wire from the light switch and now all my electrics (except the dash lights obviously) work great. An excellent photo with pin-out labels is from Ecklers. (Google "Ecklers Classic Chevy light switch 1955".) Maybe what I should do is put a toggle switch on the hot gray wire between the fuse panel and the light switch. This may not be the "correct" solution, but it should solve the problem. I called Danchuk today and tried to pick their brain. No success. I will call again tomorrow to give them more info, plus call my vendor, Ol '55. They usually have excellent tech info. As far as the dome light is concerned, I have two black wires with female connectors coming from the dome light unit down to the light switch. The bulb has two tits. I don't know where the wires should be plugged to because they are the wrong color and the schematic shows a white wire going to the ground tab on the light switch. Not wanting to burn the truck up, I will either live without a dome light for now or run a brand new manually controlled light circuit from the fuse panel. I hope I didn't confuse you too much. Cheers.
 

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The 55/56 light switch listed looks the same.
The dome light takes a two tit globe it uses a hot wire( orange) directly to the housing, then the return white wire runs to the door switches which provides a ground when the door is open allowing the globe to light up.
You also need to check your fuse panel to make sure that the correct wiring is in the right place.

The wiring to the 55/56 colors are different.

Heres the two below 55 first then 56:




 

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Trifive Automotive Electrical Wiring Expert
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2) always hot gray wire from fuse panel to correct male tab on light switch, then another hot gray wire to instrument panel lights.
The gray wire should NOT be hot all the time, only when the light switch is pulled out to the first or second position. The gray wire from the light switch supplies power to the fuse panel terminals so other dash lights ( such as clock, radio, heater control, ect) can be connected to the terminals on the fuse panel. The terminals in the corner of the fuse panel should be isolated from all other voltage and only have the varying voltage going through it from the dash light dimmer rheostat.
You have a back circuit coming from the fuse panel. ....http://www.trifive.com/garage/56%20Chevy%20Assembly%20Manual/110-18.gif
 

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As far as the dome light is concerned, I have two black wires with female connectors coming from the dome light unit down to the light switch. The bulb has two tits. I don't know where the wires should be plugged to because they are the wrong color and the schematic shows a white wire going to the ground tab on the light switch. Not wanting to burn the truck up, I will either live without a dome light for now or run a brand new manually controlled light circuit from the fuse panel. I hope I didn't confuse you too much. Cheers.
The bulb has to be a double tit single filement bulb #94 or #1004. Connect one wire to the ground (white wire) terminal of the switch and the other to the orange (stoplamp) terminal along with the orange wire that's already there. It doesn't matter which wire goes to which terminal.
 

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Discussion Starter · #9 ·
The gray wire should NOT be hot all the time, only when the light switch is pulled out to the first or second position. The gray wire from the light switch supplies power to the fuse panel terminals so other dash lights ( such as clock, radio, heater control, ect) can be connected to the terminals on the fuse panel. The terminals in the corner of the fuse panel should be isolated from all other voltage and only have the varying voltage going through it from the dash light dimmer rheostat.
You have a back circuit coming from the fuse panel. ....http://www.trifive.com/garage/56%20Chevy%20Assembly%20Manual/110-18.gif
1). Thanks for the info and diagram. I'll check the fuse panel to see where the gray wire gets its power from. 2). I have no orange or white wire to dome light. Both are black. That's what makes me confused (not hard to do!) about the wiring. When I get a chance, I'll run a continuity check on the wires to the dome light. Maybe a previous owner re-wired it.
 

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Discussion Starter · #11 ·
To acardon and others who have replied: After reading, evaluating and acting on my comments and your suggestions where applicable, I cannot help but draw one conclusion about the idea of backfeed. The tail lights work on one simple principle: the light switch activates a circuit that has only one wire. It goes from the tail light tab on the light switch directly to the tail lights. Plain and simple. I ran a new dedicated 14 ga. wire straight from said switch to an insulated junction box, then ran separate 16 ga. wires from the junction to each tail light. Then make sure I've got a good ground from each light back to the battery negative. Done. Like I said in the beginning: it ain't rocket science. I've wired lights and other accessory circuits many many times. There is no possible way that any kind of electricity (or continuity when the battery is disconnected) should be able to find its way from the dash light tab to the tail light tab like I've experienced except from inside the switch. Anyhow... I installed an insulated in-line toggle switch on the bottom of the dashboard controlling the power between the gray wire and the dash light tab on the light switch. When the circuit is open (off), everything is good. When the toggle is closed (on) and I pull the light switch out to either the parking or headlight position I have dimmable dash lights plus normal tail lights. I will see Danchuk this weekend at the Syracuse show and also see what Amercan Autowire's take is on the problem as I have used a couple of their kits in my other cars and they really know electrical systems. Hopefully this thread will be available to anyone else who may have the same problem as me. Thanks again and see ya on the road! :shakehands:
 

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..... I'll check the fuse panel to see where the gray wire gets its power from ....
When the circuit is open (off), everything is good. When the toggle is closed (on) and I pull the light switch out to either the parking or headlight position I have dimmable dash lights plus normal tail lights.



The gray wire should get power from the light switch dash tab, not the fuse panel. You needed to isolate the gray wire circuit from external power, not the tail lights. The gray wire tabs on the fuse panel is apparently getting power from some other source instead of the light switch rheostat. Are there other gray wires on the fuse panel, going to aftermarket gauges or other devices that may be backfeeding power to the gray wire circuit. If so, remove them one at a time to determine the source.
 

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Discussion Starter · #13 ·
The gray wire should get power from the light switch dash tab, not the fuse panel. You needed to isolate the gray wire circuit from external power, not the tail lights. The gray wire tabs on the fuse panel is apparently getting power from some other source instead of the light switch rheostat. Are there other gray wires on the fuse panel, going to aftermarket gauges or other devices that may be backfeeding power to the gray wire circuit. If so, remove them one at a time to determine the source.
Don, thanks for sticking with this and responding. I'll do what you suggest plus either take a photo or make a sketch of the fuse panel and wires going into or out from it. The gray wire is now connected to a "going out from" side of a fuse on the bottom strip of the fuse panel. I purchased the truck with the fuse panel wired as is so I assumed the truck was originally/correctly wired that way. Maybe not? I'll get back to you hopefully before I leave for the Syracuse show. But this still does not explain how the tail light circuit is receiving (or feeding) power to the dash lights... especially after I rewired the entire tail light circuit. Also remember from one of my above posts that I got the same results when I swapped the wires from the parking light tab, which I also rewired from scratch.
 
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