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Brake Light Issue

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Old Apr 25, 2017 | 01:06 PM
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Brake Light Issue

Hello all,

So I've done some searching and digging before posting this, and I really don't want to take it to a shop but it's looking like I will have to.

I have no brake lights. Every other light work including the running lights for night driving - the bulbs light up, just not when I brake. I've got a new brake light switch and bulbs, and am very confused on how to proceed. I want to get back on the road ASAP.

Any and all help is appreciated!
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Old Apr 25, 2017 | 03:33 PM
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From: Tracy, CA
Car: '87 IROC
Engine: LB9
Transmission: TH700R4
Re: Brake Light Issue

1. Check the Stop/Haz fuse. Hint: If the 4-way (emergency flashers) flashers work, the fuse is OK.

At the stop light switch:

2. Check for 12 volts at the orange wire.

3. If you have 12 volts there, check for 12 volts at the light blue wire (press the brake pedal).

There might have been wire color changes from '87 to '89. You might want to confirm the wire colors at Austin 3rd Gen:

http://www.austinthirdgen.org/index.php?pid=19
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Old Apr 25, 2017 | 05:37 PM
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Re: Brake Light Issue

Originally Posted by paulo57509
1. Check the Stop/Haz fuse. Hint: If the 4-way (emergency flashers) flashers work, the fuse is OK.

At the stop light switch:

2. Check for 12 volts at the orange wire.

3. If you have 12 volts there, check for 12 volts at the light blue wire (press the brake pedal).

There might have been wire color changes from '87 to '89. You might want to confirm the wire colors at Austin 3rd Gen:

http://www.austinthirdgen.org/index.php?pid=19
Fuse is good, I will have to test for proper voltage. Thank you for your help. Any other ideas of what it could be?
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Old Apr 26, 2017 | 09:54 AM
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Re: Brake Light Issue

Check this post out. Maybe the wiring diagrams can give you a bit of insight.
https://www.thirdgen.org/forums/memb...ml#post5917732
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Old Apr 26, 2017 | 04:11 PM
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From: Tracy, CA
Car: '87 IROC
Engine: LB9
Transmission: TH700R4
Re: Brake Light Issue

Originally Posted by That Sky Guy
Fuse is good, I will have to test for proper voltage. Thank you for your help. Any other ideas of what it could be?
The first thing to confirm is that the bulbs are getting 12v when the brake pedal is depressed (not in the Zoloft sense of the word).

The checks I posted will confirm that 12v is getting to and through the brake light switch.

I should have posted a step that would save you some time (my apologies):

After checking the fuse, pull one of the stop light bulbs and check for 12v at the socket while depressing the brake pedal (leave the headlights off). One of the two contacts in the socket should have 12v.

If there's voltage at the socket, see if there socket has ground; set your meter to measure resistance (ohms) and probe from the socket wall to an unpainted spot on the body (you don't need to depress the brake pedal for this test. You should read zero ohms if there's ground.
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Old Apr 26, 2017 | 06:04 PM
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Re: Brake Light Issue

Take a look under the steering column at the brake light switch. It is always pushed in when the brake pedal is in the resting (up) position. When you push down, the brake light switch pushrod extends out from spring pressure and passes power through the switch.

There are only two items that can cause all the brake lights not to come on- the fuse and the switch. If the fuse is good, then I'll bet your switch failed.
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Old Apr 27, 2017 | 01:17 PM
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Re: Brake Light Issue

Originally Posted by Tootie Pang
Take a look under the steering column at the brake light switch. It is always pushed in when the brake pedal is in the resting (up) position. When you push down, the brake light switch pushrod extends out from spring pressure and passes power through the switch.

There are only two items that can cause all the brake lights not to come on- the fuse and the switch. If the fuse is good, then I'll bet your switch failed.

Funny thing is, I checked both - switch is fine and so is the fuse. It's a brand new switch with no obvious defects. I'll make sure to inspect it again, though.
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Old Apr 27, 2017 | 03:16 PM
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Re: Brake Light Issue

Originally Posted by That Sky Guy
Funny thing is, I checked both - switch is fine and so is the fuse. It's a brand new switch with no obvious defects. I'll make sure to inspect it again, though.
When you replaced the switch, did you just slap it in there or did you adjust it?

See attachment. The adjustment should be the same for '89 model year.
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