1954 Mercury Tail Lights

JMFL36

JMFL36

Senior Member
Hey guys. I'm continuing to chase little gremlins out of a '54 Mercury I picked up a couple of years ago. This time its the tail lights. My tail lights do not turn on with the light switch, in either the parking lights position or the headlights position. The front parking and headlights work as they should, as do the brake lights and all 4 turn signals. The weird thing is that my tail lights turn on when I open a door or pull out the dome light knob. (The '54 Mercury has a separate knob for the dome lights. The 3-position pull knob for the parking and headlights is on the left side of the steering column console, and the 2-position pull knob for the dome lights is on the right side of the steering column console.)

Before I pull the dash apart I'm trying to figure out if the tail lights are just wired to the wrong switch or if its something more involved. Are the tail lights supposed to turn on when a door is opened? Is it some kind of safety thing? My '54 shop manual schematic of the dome light circuit shows no connection to the tail lights. (The bottom circuit in the photo.)
 

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dmsfrr said:
Tail-lights wired to the wrong switch would be my first guess.
Click to expand...

If you follow the red arrows, it will show you where the wires to the tail lights go. Hope this helps.
 

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As I recall when I replaced all wiring harnesses in my Sun Valley there are bullet connectors for the rear harness and the rail lamp harness behind the driver side quarter panel trim. The feed wires for the tail lights and rail lamps might be reversed. If you have electric windows these wires would be in the same location and could add to the confusion as to what is connected to which harness.
 
Thanks Lanny. Turns out the dome rail lights wire was plugged into the tail lights at that location just as you suspected. I switched that bullet connector and now all my dome lights work. But there was no other wire to plug into the tail lights there. So I guess I need to trace it from the back of the light switch.

What is the best way to get access to the back of the light switch, where all the connections are? Laying on my back in the driver's footwell, I can't see the back of the switch. I took the top cover off the steering column console, but I can't seem to access the switch from there either. Any tips would be appreciated.
 
JMFL36 said:
Thanks Lanny. Turns out the dome rail lights wire was plugged into the tail lights at that location just as you suspected. I switched that bullet connector and now all my dome lights work. But there was no other wire to plug into the tail lights there. So I guess I need to trace it from the back of the light switch.

What is the best way to get access to the back of the light switch, where all the connections are? Laying on my back in the driver's footwell, I can't see the back of the switch. I took the top cover off the steering column console, but I can't seem to access the switch from there either. Any tips would be appreciated.
Click to expand...

Disconnect the battery and remove the light switch, not hard to do at all.
 
John, there is another bullet connector(maybe a double) deep inside the trunk on the driver side near the front edge of the wheel well. That is where the tail light harness plugs into rear body harness that comes in from the front. I believe that the trunk lamp also plugs in at this location. I will check my spare dash today regarding access to the light switch but I think that the trunk business will solve your problem. Later!
 
Lanny, I know the fault is somewhere between the light switch and the bullet connector at the driver's cowl. My tail lights were working, but they were incorrectly wired to the dome lights switch with the wire that is supposed to go to the dome rail lights. I switched the bullet connector at the driver's cowl and now all the dome lights work as they should. Now I just need to find the lead that's supposed to go from the parking/headlight switch to the tail light harness wire at the driver's cowl.
 
John look for the black wire from the light switch that connects to the black wire to the tail lights near the cowl above or near the e-brake handle. There should be a bullet connector there on one end or the other.
 
Yes, I know which wire I'm looking for and where it goes. I can see the bullet connector at the black wire on the driver's cowl leading to the tail light harness, but it is empty - no wire coming from the dash to it. I just need some advice on the best way to access the back of the light switch in the dash.
 
John, I just looked at my old, spare dash and this is what I found. The switch has 6 terminals and 5 of the wires go into a loom. The remaining wire which appears to be black (original and deteriorating) is long enough to terminate where you are looking but it joins another wire at the bullet, making 2 wires joining at that point. The second wire has been nipped so I don't know its source or termination or its function. Maybe you can find it with this info. The switch is accessed from the bottom of the control panel by removing 2 small cap screws located up in the inside of the rectangular recessed opening of the panel below where the switch control rod is located. When the rod is removed from the front and the 2 cap screws are removed the switch should be able to tip a little to the rear and come out and down. The repair manual doesn't show anything.
 
Thanks Lanny. I have the same 2 wires connected together in that bullet. One wire is black, the other is black with red tracer. The black wire goes to the parking/headlight switch and has good continuity. The black with red tracer wire goes to the engine compartment where it ends in a loose bullet connector along the driver's inner fender, and is not connected to anything. There is no black w/red wire shown on the exterior lights circuit in my shop manual. Wonder what else would be wired to the parking lights circuit?

I have removed the light switch and will be testing it tomorrow.
 
John, the pics I saw of your car seem to show it has an auto trans. If that is the case, my repair manual shows a black with red tracer for the lamps(s) in the auto trans selector indicator on the column head. I will look further in my wiring diagrams to see if I can find anything else. There is a possibility that the wire to the front may go to the back-up light switch located in the steering column below the master cylinder. Later!
 
Thanks Merc_Cruzer and Lanny for the info. I tested the light switch and its leads this morning. No voltage to the light switch at the parking light power lead connector. So I traced that yellow/red tracer wire back to the circuit breaker bus bar and found a loose connection where the yellow/red tracer wire connects. Cleaned and tightened that connection and now have good voltage at the light switch, and the parking lights work as they should now. Yay!

So to recap, instead of tracing the problem to its source, the previous owner had switched the tail lights wire with the dome light wire so he could manually switch on the tail lights with the dome light switch. Geez!
 
John, the p.o. mush have been a moonshiner! Turn off the tail lights, disconnect the brake lites at the master cylinder and go like the wind. Glad I could help. Lanny
 
One other thing I wanted to mention. In my '54 Mercury shop manual, the exterior and instrument lights schematic (attached) shows 5 bulbs for the automatic transmission selector on the steering column. My selector has just a single bulb that moves with the selector to illuminate the current position of the selector (P R N D 2). I don't know if this is an error in the shop manual or if other models for '54 have a different selector setup.
 

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