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Brake Lights Won't Come On

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Old 06-07-2014, 10:36 AM
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Brake Lights Won't Come On

I have a 1990 Z32 and I know what you're thinking by the title, that it's the brake light switch. But it's not, not unless the parts store sold me a defective switch (which I know is fairly common.) So let me tell you my issue, the brake lights in the tail lights aren't coming on even though the third mounted brake light on the hatch back does. Now I've had the car a while so and they used to work just fine so I know the bulbs I have in are the correct ones. But I replaced the brake light switch and I'm still having the same issue. The running lights and blinkers all work just fine, just not the brake lights in the tail lights. Can someone give me some idea as to what it could be, is there another switch or sensor that I'm missing? I've checked all the fuses under the hood and under the dash and I didn't see any specific fuses for the brake lights. I'm pretty sure there's a problem with the wiring but I looked at all the leads going to the tail lights and nothing stands out. Any suggestions would be greatly appreciated!!
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Old 06-07-2014, 11:03 AM
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Bad ground wire?

The working Dole light indicates the brake light switch is working as designed. Have you had work done on the back of the car? I suggest you start with the basics. Pull the socket assemblies and use a meter to check for voltage on hot side of the bulb sockets and also check for connectivity on the ground side. That will tell you which side of the circuit you need to trace back on. I suspect there is a common ground wire on the brake lights that has come loose. Obtaining a copy of the FSM electrical schematics will help you with tracing the circuits through the car.
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Old 06-07-2014, 11:22 AM
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Thanks! There's been no accident or work done in the rear area of the car and I checked what grounds I saw but I'll check the sockets next. Is it possible for the tail light sockets to work with out full connectivity on the hot side or the ground?
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Old 06-07-2014, 11:42 AM
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Originally Posted by RaegingZ32
Is it possible for the tail light sockets to work with out full connectivity on the hot side or the ground?
No. The wire harness for the brake lights, including ground wires, are likely hiding under the rear interior panel.
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Old 06-07-2014, 01:26 PM
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Originally Posted by ken99
No. The wire harness for the brake lights, including ground wires, are likely hiding under the rear interior panel.
I've looked at all the wires behind the rear panel, including the ground and it all looks good...I'm still not able to figure it out=\
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Old 06-07-2014, 03:16 PM
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Originally Posted by RaegingZ32
I have a 1990 Z32 and I know what you're thinking by the title, that it's the brake light switch.
Are you talking about the "taillight sensor"? Located near the passenger side taillights. My taillights wouldn't turn on but my brake lights were working, all bulbs were fine. I took that little box apart and one of the fuses was busted inside so I replaced it and everything works now.
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Old 06-07-2014, 07:52 PM
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Originally Posted by Rupe
Are you talking about the "taillight sensor"? Located near the passenger side taillights. My taillights wouldn't turn on but my brake lights were working, all bulbs were fine. I took that little box apart and one of the fuses was busted inside so I replaced it and everything works now.
A blown fuse in this box is the likely culprit. I always assumed the Dole circuit fed from this sensor box as well as the standard brake lights. The Z32 circuit diagram indicates the Dole light gets voltage directly from the brake light switch. A blown fuse in the sensor box would kill the rear brake lights, but not affect the Dole light. Good suggestion by Rupe.

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Last edited by ken99; 06-07-2014 at 08:04 PM. Reason: added cropped brake circuit image
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Old 09-30-2014, 09:04 AM
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pull it and have it tested
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