'65 brake light switch functioning in reverse
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Racer
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'65 brake light switch functioning in reverse
The brake lights stopped working on my buddy's '65. He removed the brake light switch from its mounting flange and found no current feeding to it at all. Now, if we jump a wire to it, the brake lights go on with the switch button pushed, off when released--opposite of how it's supposed to work. He got a cheap plastic replacement and the same is the case with that. He also recently replaced the turn signal switch, but I can't see how that could cause this. Ideas?
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The first thing I would check it to see if some wires got switched. Maybe he had a connector apart and got the spades in the wrong slots.
Last edited by woodsdesign; Jan 13, 2019 at 05:40 PM.
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Well, the TS switch could cause this problem as the brake light signal goes through the TS switch. The turn signal switch actually flashes the brake lights. I would start there looking for a short or miswired connection.
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Measure voltages. You should always have 12v on the orange wire going to the switch, as long as the battery is connected. You should never have 12v on the white wire
going from the other side of the switch to the turn signal UNLESS the brake pedal is pushed (plunger on switch extended). There's no way it can work the way you describe it unless the switch you're using is internally wrong. It should read zero ohms (shorted) with the plunger out (brake on) and infinity (open) with the switch plunger depressed (brake off)
NOTE: Those two wires can also be black with orange stripe and black with white stripe on some cars.
going from the other side of the switch to the turn signal UNLESS the brake pedal is pushed (plunger on switch extended). There's no way it can work the way you describe it unless the switch you're using is internally wrong. It should read zero ohms (shorted) with the plunger out (brake on) and infinity (open) with the switch plunger depressed (brake off)
NOTE: Those two wires can also be black with orange stripe and black with white stripe on some cars.
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switching the orange/white feeds would reverse the polarity, but shouldn't have anything to do with the fact that the lights are going on when the plunger is depressed and off when extended, as far as I can see. Even within the TS switch, it just relays the current through the white wire to the 2 taillights, so I can see it failing to do that, but not somehow inverting the function. I'm sure there's something simple that I'm overlooking.
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Switching the wires on the switch won't do anything, it will still work the same. Disconnect the two wires at the switch and touch them together. The brake lights should come on. Pull the wires apart and the lights should go off. That's all the switch does. You're overlooking a symptom or your switch is normally closed when it should be normally open. It should have continuity across the two contacts ONLY when the plunger is NOT pushed in. It should be an open circuit when the plunger is pushed all the way in. It's about as simple a circuit that can be created.
Try shorting the two wires and post back what happens.
Try shorting the two wires and post back what happens.
Last edited by 65GGvert; Jan 13, 2019 at 10:07 PM.
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The problem is not in the brake switch. It is in the TS switch or the tail lights.
Try this. Turn on the headlights switch so the tail light come on. When you depress the brake switch, do all the bright tail light filaments go off? Are there any noticeable differences in brightness? With the tail lights still on, put the TS switch to the right and observe and then the left. What do you see?
Try this. Turn on the headlights switch so the tail light come on. When you depress the brake switch, do all the bright tail light filaments go off? Are there any noticeable differences in brightness? With the tail lights still on, put the TS switch to the right and observe and then the left. What do you see?
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The problem is not in the brake switch. It is in the TS switch or the tail lights.
Try this. Turn on the headlights switch so the tail light come on. When you depress the brake switch, do all the bright tail light filaments go off? Are there any noticeable differences in brightness? With the tail lights still on, put the TS switch to the right and observe and then the left. What do you see?
Try this. Turn on the headlights switch so the tail light come on. When you depress the brake switch, do all the bright tail light filaments go off? Are there any noticeable differences in brightness? With the tail lights still on, put the TS switch to the right and observe and then the left. What do you see?
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Army
If the problem is in the TS, he has more than one problem. Otherwise pushing the brake switch plunger in wouldn't make the brake lights come on and letting it out wouldn't make them go off. All the brake switch does is pass the 12v up to the turn signal switch. As I said from the start, I think there's a misinterpretation of what is happening when you move the switch plunger.
The brake light switch is a simple switch in series with the brake lights 12V wire that is closed when the brake pedal is pushed.....when the brake pedal return spring holds the plunger in the switch is open... A simple ohmmeter check of the switch terminals while working the plunger will determine if the switch is correct.
Last edited by Frankie the Fink; Jan 14, 2019 at 06:54 AM.
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Oh contrare! First of all, we have to believe that the symptoms and testing as reported is correct which is always questionable. Particularly that “it was the same brake switch that worked properly before and he even tried a new one with the same result”. As all have correctly said, it is the simplist of switches, When depressed, the switch is open and the lights are off, when released the switch is closed and the brakes are on. The OP was asked to check this and hasn’t responded, but if this is true, the switch is fine, so we move down the circuit following current flow. Next is the TS switch.
Since we can’t be there and must try to troubleshoot solely on the observations provided and we were told that the TS switch was replaced, it becomes suspect as do the taillights themselves. For example, a missing ground in one dual filament rear bulb allows the signal on the other filament to bleed over, hence why I said report back on the symptoms and if they change when you turn on the tail lights. As for the TS switch, the brake light signal is supposed to pass directly through when the switch is off with no impact. If there is no issue with the grounds in the rear lights, the TS switch or wiring (perhaps disturbed when the new switch was installed) becomes the culprit.
This actually should be an easy fix. I look forward to the OP reporting back.
Since we can’t be there and must try to troubleshoot solely on the observations provided and we were told that the TS switch was replaced, it becomes suspect as do the taillights themselves. For example, a missing ground in one dual filament rear bulb allows the signal on the other filament to bleed over, hence why I said report back on the symptoms and if they change when you turn on the tail lights. As for the TS switch, the brake light signal is supposed to pass directly through when the switch is off with no impact. If there is no issue with the grounds in the rear lights, the TS switch or wiring (perhaps disturbed when the new switch was installed) becomes the culprit.
This actually should be an easy fix. I look forward to the OP reporting back.
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Army
Gone as far as I'll go with the info given.... the initial thread talks about a jumper test - from where ? to were ?
If its from a 12V fixed source to a brake light switch terminal then the turn signal circuit is eliminated and the switch is somehow the culprit...
If its from a 12V fixed source to a brake light switch terminal then the turn signal circuit is eliminated and the switch is somehow the culprit...
Last edited by Frankie the Fink; Jan 14, 2019 at 08:25 AM.
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Oh contrare! First of all, we have to believe that the symptoms and testing as reported is correct which is always questionable. Particularly that “it was the same brake switch that worked properly before and he even tried a new one with the same result”. As all have correctly said, it is the simplist of switches, When depressed, the switch is open and the lights are off, when released the switch is closed and the brakes are on. The OP was asked to check this and hasn’t responded, but if this is true, the switch is fine, so we move down the circuit following current flow. Next is the TS switch.
Since we can’t be there and must try to troubleshoot solely on the observations provided and we were told that the TS switch was replaced, it becomes suspect as do the taillights themselves. For example, a missing ground in one dual filament rear bulb allows the signal on the other filament to bleed over, hence why I said report back on the symptoms and if they change when you turn on the tail lights. As for the TS switch, the brake light signal is supposed to pass directly through when the switch is off with no impact. If there is no issue with the grounds in the rear lights, the TS switch or wiring (perhaps disturbed when the new switch was installed) becomes the culprit.
This actually should be an easy fix. I look forward to the OP reporting back.
Since we can’t be there and must try to troubleshoot solely on the observations provided and we were told that the TS switch was replaced, it becomes suspect as do the taillights themselves. For example, a missing ground in one dual filament rear bulb allows the signal on the other filament to bleed over, hence why I said report back on the symptoms and if they change when you turn on the tail lights. As for the TS switch, the brake light signal is supposed to pass directly through when the switch is off with no impact. If there is no issue with the grounds in the rear lights, the TS switch or wiring (perhaps disturbed when the new switch was installed) becomes the culprit.
This actually should be an easy fix. I look forward to the OP reporting back.
Last edited by 65GGvert; Jan 14, 2019 at 08:47 AM.
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Thanks for all the input, guys. I'll relay it along and post back the outcome. It may be a few days before my friend has time enough to get at it again. I will 1st have him directly supply current to the white wire coming out of the BS to confirm whether lights work properly that way, which should confirm or eliminate problems with the TS switch or lights/grounds. Also, a direct test of the switch itself is simple enough. It seems impossible that both of those would be working properly, given the symptoms. Unfortunately, I'm stuck in a wheelchair, so I can't just go try do these things myself, which drives me a little nuts when stuff like this comes up.
Last edited by klavrack; Jan 14, 2019 at 08:45 AM. Reason: typo
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Thanks for all the input, guys. I'll relay it along and post back the outcome. It may be a few days before my friend has time enough to get at it again. I will 1st have him directly supply current to the white wire coming out of the BS to confirm whether lights work properly that way, which should confirm or eliminate problems with the TS switch or lights/grounds. Also, a direct test of the switch itself is simple enough. It seems impossible that both of those would be working properly, given the symptoms. Unfortunately, I'm stuck in a wheelchair, so I can't just go try do these things myself, which drives me a little nuts when stuff like this comes up.
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What he told me is that the orange input to the BS had no juice, so he ran a temp wire from a live terminal on the fuse block. Whether it was an ignition-on-only-hot terminal he didn't tell me. He just said when power was supplied to the BS and the regular output wire was connected, brake lights went on when plunger was depressed and off when released. When he next gets time to mess with it, I'll confirm all this and try the checks suggested by you and others, hopefully sometime later this week.
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Army
What he told me is that the orange input to the BS had no juice, so he ran a temp wire from a live terminal on the fuse block. Whether it was an ignition-on-only-hot terminal he didn't tell me. He just said when power was supplied to the BS and the regular output wire was connected, brake lights went on when plunger was depressed and off when released. When he next gets time to mess with it, I'll confirm all this and try the checks suggested by you and others, hopefully sometime later this week.