Stop lights still not working 40 coupe

Fordyguy

Fordyguy

Junior Member
Recently I replaced stop light switch but I still don’t have any brake lights. I ran new ground wires from housing to frame. I put in new 1157 bulbs and making good contact. Both leads are hot and both filaments are lit when I turn on my lights. Still no brake lights. I have double checked all wiring.
 
So, if I understand correctly, when you turn on the lights, BOTH filaments in the (incorrect 1157) bulbs light up?
If that's the case, you have some wiring out of place.

With the lights on, only one filament should light.
Perhaps have someone else double check. At times, a different set of eyes is all it takes to find the issue.
 
it's almost impossible to trouble shoot electrical issues with out a VOM or at least a light probe. I would start with checking voltage to one side of the switch and go from there.
 
If both lights work something is wrong as stated, do you have a directional signal ?
If so check that wiring and flasher .
What happens when you put a jumper between the two leads on the brake light switch?
 
1157 Is a 12V light bulb and will not work on 6V properly. What tool are you using to test with? voltmeter or test light or power probe?
 
My car has been converted to 12 V I do not have turn signals and I have not changed any wiring. It has been working fine for 10 years my Brake lights stopped working, so I switched out the brake light switch and that didn’t fix my problem. My dad got to looking at it and I think maybe he crossed some wire somehow While checking it out I have been through it to three times and I can’t find anything wrong. I did run new ground wires from the housing to the frame just because the old ones look bad., When I run a jumper wire between the two wires at the switch, I have nothing unless I turn the headlights on. When the lights are on, Both filaments are lit and the bulbs which I know it should only be one. Thank everyone that has responded
 
You ran a new ground from housing to frame; great. Now check to verify a good ground between the lamp holder and the housing/chassis ground. A problem with that on either side can cause weird problems, like both tail light and brake light showing voltage when the headlights are turned on.
 
I think you either have a bad ground or a short/broken green wire.


With the headlight switch and brake light switches off, check for 12V at the purple junctions below.


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Glenn is correct. I'll add, the brake light wire to the switch, green, should be hot all the time
 
Your wiring is not original. Originals do not have ground wires at the rear lights they use the ground from being bolted to the fender. It appears someone wired your stop lights into the head light switch. as you can see above the green wire from the stop lights goes to the brake master cylinder stop light switch. From the stop light switch another green wire goes to the light circuit breaker. That wire should be energized all the time. Do you have the light circuit breaker? Is your wiring plastic coated or cloth covered and color coded?
 
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The wires on the circuit breaker are hot all the time with switches off. The wires are Cloth covered and color coded. The headlight switch has pigtail soldered to the switch. They appear to be connected to the right color wires. I am not getting any power to my brake light switch now without the headlights being on. I tested the ground on the tail lights on the socket And both elements are hot if the headlights are on. Nothing when they are off.
 
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Sounds to me like the constant hot for the brake light switch is somehow going to the headlight switch rather than to the brake light switch. Is there a solid green wire going to the headlight switch or dimmer switch?
 
Fordyguy said:
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The wires on the circuit breaker are hot all the time with switches off. The wires are Cloth covered and color coded. The headlight switch has pigtail soldered to the switch. They appear to be connected to the right color wires.I am not getting any power to my brake light switch now without the headlights being on. I tested the ground on the tail lights on the socket And both elements are hot if the headlights are on. Nothing when they are off.
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Now you need to trace the "green"wire or whatever color it is, FROM the brake light switch back to the circuit breaker.


Re, "Sounds to me like the constant hot for the brake light switch is somehow going to the headlight switch rather than to the brake light switch"


He has NO power to the brake light switch with both switches off.
 
I would first turn your VOM to the lowest Ω (ohm) value on your meter and check it from the stop light switch back to the circuit breaker. Do the same for the headlight switch.
 
The horn, brake light, and starter circuits are all wired direct to the battery in one way or another. They will all function with the ignition switch off. All the old Fords were wired this way. If the power only comes on with the light switch then it's not wired correctly. The brake light power should be wired to the circuit breaker under the dash. The brake light switch is then wired back to the brake light filaments of the 1157 bulbs. The light switch on the dash was new for 1940. It also can function without the ignition switch. Prior to that, it was down on the bottom of the steering column. Eventually, the dome light was wired to the light switch but it was also independent in that time frame.

As was mentioned previously, the ground path was originally through the sheet metal and frame of the car. Jumpers are only necessary when the ground path deteriorates till electrical flow can't take place. A jumper will get it working as long as it is connected to a good ground source but it's a band aid fix to the actual problem. The tail light is wired to the light switch for both road lighting and park lighting but it's connected to the low candle power part of the 1157 bulb. The brake light switch is connected to the higher candle power filament in that bulb.
 
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There are a bunch of connectors between the wiring harness coming into the engine compartment through the firewall. There the green wire should connect to the green going back to the brake light switch and the I am guessing that at that location, the green wire is reversed with something else, like the black+green high beam or black+red low beam. Check and see if you get voltage to the brake light switch with high beam or low beam.



And you still need to confirm that the actual tail+brake light bulb sockets (not the hot contacts inside the socket) have a good zero Ohm ground to the chassis.
 
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