The GREAT Ms. American 3.14159's Left Brake Light Won't Light Mystery Caper

[JCAllison]

Hey all,
Have something mysterious going on with Ms. American's Left Brake Light.

When the Headlights are on, both Tail Lights come on.

When the Turn Signals are activated, both Tail Lights come on (separately, of course).

But when the Brake Pedal is activated, only the Right Brake Light comes on!

The Right Brake Light is at the end of the circuit, so the circuit has electricity.

Also, the Left Turn Signal shares the same filament with the Left Brake Light, and as mentioned above, the Left Rear Turn Signal works.

Don't know why the Left Brake Light won't light.

Any suggestions?

Hope this finds you all doing well, and staying safe.

JC Allison

[Lanny]

I would think it has to be something with-in the turn signal switch causing it.

Have someone look at the brake lights, and see if the left one comes on and
stays on if you just wiggle the blinker lever ever so slightly.




.

[dmsfrr]

Originally Posted by Lanny

I would think it has to be something with-in the turn signal switch causing it. ...

That would be my first guess too, a poor connection inside the turn signal switch.

[marko39]

Swap bulbs and see if it stays the same. Easy to do and rule out a bulb issue.

[Zeke3]

If you have the taillights on and then apply the brakes, does the left taillight stay on or go off? If the taillight also goes off indicates an issue with the ground connection for that lamp.

[estout81]

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Turn signal switch. Had the same problem on my '51 Ford.

[Daves55Sedan]

Originally Posted by JCAllison

When the Headlights are on, both Tail Lights come on.

GOOD, as long as the tail-lights are the "low" brightness filament.

Originally Posted by JCAllison

When the Turn Signals are activated, both Tail Lights come on (separately, of course).

GOOD, as long as the tail-lights are the "High" brightness filament.

Originally Posted by JCAllison

Also, the Left Turn Signal shares the same filament with the Left Brake Light, and as mentioned above, the Left Rear Turn Signal works.

That is correct. The brake light uses the same filament as the turn signal light, that way you can see the turn signal at night since it is brighter than the tail-light "low" filament.

Originally Posted by JCAllison

But when the Brake Pedal is activated, only the Right Brake Light comes on!

So, we have already determined that the "high" brightness filament works, by testing the turn signals, right? Remove the red lens and carefully jiggle the bulb (best to do this in dim light or darkness so it's easier to see the light come on in the bulb). Does the light work when jiggling the bulb while someone else is pushing on the brake pedal? If so, the inner surface of the bulb socket may be partially corroded, or the bronze plated surface of the bulb base may be corroded and need cleaning. If so, brush off with fine steel wool and coat both surfaces with hi-dielectric silicone compound.
If the bulb and socket are not at fault, look at the wiring connector ahead of the bulb and identify the "high" brightness wire. Unplug it and inspect connectors for corrosion. Clean and coat with silicone grease and reconnect and test again.

[Daves55Sedan]

There may be an issue at the wiring junction-block under the dashboard immediately downstream of the turn-signal wiring harness. Notice how the two wires from the controls (brake-light switch and turn-signal switch) come back out the other end as ONE wire which goes to the back of the car for the lights?
If you know your cars wiring color-code, identify the incoming wire into the junction block from the brake light switch and disconnect/clean and plug back in. The one wire going out of the switch to the back of the car should be good since we know that at least one of the "high" brightness elements is working.

[5851a]

It is the switch I would bet. The switch makes or breaks the contacts and circuit. Lot of things going on in the switch and none of them have anything to do with parking lamps, they are on separate circuit. 2 power wires enter the switch, one of them is power when brakes are applied with full time power and other is ignition/accessory power through signal flasher. What direction the signal lever is turned to the switch turns off the brake lamp to that side and is powered by the flasher/ignition circuit wire. It also separates the front turn signals dashboard indicators from the rear so front turns don't illuminate during braking. Your only intermittent repeatable illumination failure points to the signal switch. NOS seems to be quite expensive and the fishing of wires through the column can be a task. It may be disassembled cleaned and reassembled with adjustments made to contacts. You may need to find the ever elusive star lock push on lock washer.

[JCAllison]

Originally Posted by Lanny

I would think it has to be something with-in the turn signal switch causing it.

Hey Mr. L, I was hoping you wouldn't say that! Have looked up the procedure to mess with the Turn Signal Switch, and it doesn't look like an easy peasy process. But like anything else, if I don't do it, it won't get done.

Have someone look at the brake lights, and see if the left one comes on and stays on if you just wiggle the blinker lever ever so slightly.

Will give that a try. If the Left Brake Light comes on then will just have to find out why it is so tenuous.

There has appeared another anomaly regarding the Brake Lights: The Right Brake Light doesn't always go off when the car is parked after using the Brakes to stop the car in its Car Port. Just have to jiggle the Brake Pedal to get it to go off.

Anyway, thanks for taking the time to respond. Take care.

JC

[JCAllison]

Originally Posted by dmsfrr

That would be my first guess too, a poor connection inside the turn signal switch.

Hey Mr. D, It certainly needs looking into.

Have for the past three days been dealing with a semi-serious health issue, and haven't had much time to respond, but am determined to catch up on the sage advice from everyone.

Stay tuned!

JC

[JCAllison]

Originally Posted by marko39

Swap bulbs and see if it stays the same. Easy to do and rule out a bulb issue.

Hey Mr. M, there happens to be here another identical bulb (don't know the number), and two alternate bulbs (Sylvania 2387) which are supposed to be even brighter, and longer lived. This swap out will probably take place tomorrow morning before the Sun gets over to where it is shining on Ms. American's Tail Light Assemblies. Will let you know the outcome.

Anyway, take care, and stay safe.

JC

[JCAllison]

Originally Posted by Zeke3

If you have the taillights on and then apply the brakes, does the left taillight stay on or go off?

Hey Mr. Z, I don't know. Will check this tomorrow morning just before the Sun clears the Pine Trees. It's a twilight zone.

If the taillight also goes off indicates an issue with the ground connection for that lamp.

Will watch for this particular thing. Just by looking at the Bulbs here on the bench, it looks as though the Head/Tail Lights are on their own filament. In any case, will let you know how it goes.

Take care.

JC

[JCAllison]

Originally Posted by estout81

Turn signal switch. Had the same problem on my '51 Ford.

Hey Mr. E, it certainly seems to be a problem that comes with aging. Ms. American will be 58 years old on Sunday. We all seem to wear out sooner or later.

Will run the test on the Turn Signal Switch, and see how it comes out.

Stay tuned.

JC

[JCAllison]

Originally Posted by Daves55Sedan

GOOD, as long as the tail-lights are the "low" brightness filament.
GOOD, as long as the tail-lights are the "High" brightness filament.
That is correct. The brake light uses the same filament as the turn signal light, that way you can see the turn signal at night since it is brighter than the tail-light "low" filament.

Hey Mr. D, All of this is in "GOOD" condition.

So, we have already determined that the "high" brightness filament works, by testing the turn signals, right?

Right.

Remove the red lens and carefully jiggle the bulb (best to do this in dim light or darkness so it's easier to see the light come on in the bulb).

All right.

Does the light work when jiggling the bulb while someone else is pushing on the brake pedal?

Will find out in the morning.

If so, the inner surface of the bulb socket may be partially corroded, or the bronze plated surface of the bulb base may be corroded and need cleaning. If so, brush off with fine steel wool and coat both surfaces with hi-dielectric silicone compound.

It just so happens that all the stuff necessary to do this procedure is here on the shelf.

If the bulb and socket are not at fault, look at the wiring connector ahead of the bulb and identify the "high" brightness wire. Unplug it and inspect connectors for corrosion. Clean and coat with silicone grease and reconnect and test again.

Am really afraid of messing with wiring. It is so old and brittle that even minor straightening can cause cracks in the insulation (ask me how I know). In any case, will plod on doing what can be done. Thanks for heads up.

Stay safe.

JC

[JCAllison]

Originally Posted by Daves55Sedan

There may be an issue at the wiring junction-block under the dashboard immediately downstream of the turn-signal wiring harness.

Hey Mr. D, That's another place to look.

Notice how the two wires from the controls (brake-light switch and turn-signal switch) come back out the other end as ONE wire which goes to the back of the car for the lights?

Haven't a clue as to where this all is located, but will make a careful inspection to see what can be found.

If you know your cars wiring color-code,

Which I don't, but will have to learn.

identify the incoming wire into the junction block from the brake light switch and disconnect/clean and plug back in. The one wire going out of the switch to the back of the car should be good since we know that at least one of the "high" brightness elements is working.

We know that BOTH the "'high' brightness filaments' are working because both side's Turn Signals blink.

Will find out in the morning. It may even take putting in NEW Bulbs to keep both sides the same brightness.

Will keep you all updated if, when, and as progress occurs.

JC

[JCAllison]

Originally Posted by 5851a

It is the switch I would bet. The switch makes or breaks the contacts and circuit. Lot of things going on in the switch and none of them have anything to do with parking lamps, they are on separate circuit. 2 power wires enter the switch, one of them is power when brakes are applied with full time power and other is ignition/accessory power through signal flasher. What direction the signal lever is turned to the switch turns off the brake lamp to that side and is powered by the flasher/ignition circuit wire. It also separates the front turn signals dashboard indicators from the rear so front turns don't illuminate during braking. Your only intermittent repeatable illumination failure points to the signal switch. NOS seems to be quite expensive and the fishing of wires through the column can be a task. It may be disassembled cleaned and reassembled with adjustments made to contacts. You may need to find the ever elusive star lock push on lock washer.

Hey Mr. 5851, have seen this explanation previously, but don't have any idea where all these components actually are. This is the first anomaly with Ms. American's Brake Lights that hasn't been easy to remedy. Why can't anything be easy?

So with all the places to look that have been suggested, tomorrow should be a very busy day. Will keep you all updated if, when, and as progress occurs.

Stay safe everyone.

JC

[cousinjd]

If it hasnt already been mentioned, just swap bulb for bulb and observe if the same problem switches position. Just a thought. Jim

[JCAllison]

Originally Posted by cousinjd

If it hasn't already been mentioned, just swap bulb for bulb and observe if the same problem switches position. Just a thought. Jim

Hey CJD, just got back in from the Car Port, after doing some diagnostics on Ms. American's Brake Lights. What was found was that the Left Brake Light wasn't ON with the Brake Pedal Depressed. So following the good advice to check the Left Turn Signal Switch, found that the Left Turn Signal was in the "ON" position, and that if the Ignition Switch was in the "Run" or "Accessories" position, that the Brake Light WOULDN'T come ON, but the Turn Signal would blink. BUT... If the Turn Signal Wand was in the "OFF" position, that the Left Brake Light WOULD come ON. The same is true for the Right Brake Light. With the Brake Pedal depressed, and the Turn Signal Wand in the OFF position, BOTH Brake Lights come ON. Signaling for a Right Turn, turns off the Right Brake Light.

Am suspecting that Ms. American has been pulling into the Car Port with the Left Turn Signal ON, and it has not been turned off when parked.

So it appears that this whole thing was a "false alarm", because everything is working EXACTLY as it should work. Am relieved to know that everything is as it should be. Want to thank everyone for their sage input.

Anyway, hope this finds you all doing well. Take care. Stay safe.

JC

[KULTULZ]

Am suspecting that Ms. American has been pulling into the Car Port with the Left Turn Signal ON, and it has not been turned off when parked.

Do the turn signals cancel after a turn?