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Right Rear Running Light Goes Out When Braking and...

02/28/2016 12:49 PM

My friends 96 Toyota Tercel has been running like a top. It's been years since it's needed more than a glance at the fluids who's level never change and a topping off of wiper fluid.

It was a great surprise to learn that a taillight wasn't working and and even greater surprise to learn that changing the bulb wouldn't do the trick.

When the headlights are on all of the lights are working properly, but when the brakes are applied the right rear brake light does not illuminate and the running light (in the same two filament bulb) goes out as well? The drivers side lights are unaffected? What gives? It there a ground point or harness that I should pay particular attention to? I just started looking and there isn't much on line (that narrowed it down) If I need to join a Toyota forum just to get the answer I will, but I'm not there just yet.

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Guru

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#1

Re: Right rear running light goes out when braking and...

02/28/2016 1:48 PM

Have you checked it with a meter?

Sounds like a short or break in the harness.

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Guru

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#2

Re: Right rear running light goes out when braking and...

02/28/2016 2:09 PM

is the front bulb good?

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#3

Re: Right rear running light goes out when braking and...

02/28/2016 2:18 PM

This is just a guess:

It sounds like you have an open ground for your running light and stop light on that side.

The return side of both filaments are connected inside the bulb but not connected to the chassis return. When the running lights are on, the running light filament gets ground up through the brake light filament on that side, back through the brake light wiring, and down through the brake light filament on the other side to ground. When you step on the brake, that line goes to 12 volts, so there is no voltage across the running light and it goes out.

http://auto.howstuffworks.com/auto-parts/brakes/brake-repair/brake-light-wiring3.htm

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#11
In reply to #3

Re: Right rear running light goes out when braking and...

02/29/2016 12:52 PM

GA, anytime I see this weird behaviour, it is almost always a bad ground exactly for the reasons your stated.

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#13
In reply to #3

Re: Right rear running light goes out when braking and...

03/02/2016 10:18 AM

I found an open ground! thank you. The white ground wire connection to the socket must be bad. Fortunately the connection point is almost visible inside the plastic socket. I was able to jam a thin blade down inside to complete the connection.

I made a little ball of very fine copper wires and jammed it down into the crevice with some dielectric lube to hold it until a trip to the auto part store can yield a replacement socket.

Thanks again.

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#4

Re: Right rear running light goes out when braking and...

02/28/2016 2:31 PM

This is often just a broken earth connection in the light cluster. Try using a piece of wire to connect the earth in the light cluster to body ground. If that works, you can either track down the bad connection or just add a new earth.

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#5

Re: Right rear running light goes out when braking and...

02/28/2016 10:39 PM

This is a two pin,2 element bulb,with 2 indexing tabs on the brass base.

One is higher up on the base than the other.

It can be put in backwards..it will be very hard to twist,but it can be done.You will get results similar to the ones you have now if it is reversed.

Look at the socket and you will see 2 locking slots.Determine which way the bulb should go in based on the placement of the slots.

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#6

Re: Right rear running light goes out when braking and...

02/28/2016 11:41 PM

Do you use your turn signals? Sometimes, when the turn signal is used, the signal switch doesn't reset properly. That would cause the affected signal light to not illuminate. This problem shouldn't affect the tail light, but it might just be F.M.

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#7

Re: Right rear running light goes out when braking and...

02/29/2016 12:06 AM

Hot wire may be shorted to the chassis, which leads to bypassing the current and dropping the voltage.

Gajanan Phadte

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#8

Re: Right rear running light goes out when braking and...

02/29/2016 4:04 AM

Almost certainly as said in #3 and #4. If you draw a simple wiring diagram you should be able to understand the cause.

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#9

Re: Right rear running light goes out when braking and...

02/29/2016 9:23 AM

This is just another guess, yet a possibility! Check the bulb ratings on both left and right tail / brake lights. Be sure both ratings (wattage wise), are the same! If one has a higher wattage than the other, when activated may pull more current and therefore cannot supply enough for the other bulb? The left tail /brake light being in parallel with the right bulbs, causing unequal current division between the two!

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#10

Re: Right rear running light goes out when braking and...

02/29/2016 12:15 PM

There may be something here; www.toyotanation.com

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#12

Re: Right Rear Running Light Goes Out When Braking and...

02/29/2016 7:43 PM

Sounds like a poor chassis ground. Was the right rear quarter panel in an accident? As you live in Chicago, salt corrosion could also cause this. At night, turn off the lights and press on the brake pedal, do the dash lights light? Grounding the fixture may not work as, the entire quarter panel may be above ground. Do you have a meter? If yes get a long piece of wire and firmly connect it to the neg battery terminal. Connect this wire to the black meter lead and the red lead to the RR quarter panel, sand a bare spot inside the trunk. Have an assistant depress the brake pedal if the voltage goes above 2 volts you have a problem with the chassis ground. Perform the same test with the positive lead Red to the the trunk floor pan, trunk deck etc. Once you find a good piece of sheet metal ground fixture to this place using the wire you connected to the battery.

If this solves the problem, leave the car in a conspicuous location with the keys in the ignition. This prevents you from having to pay junkyard/towing fees

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