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Fredbird Brake lights...
Senior Guru
San Antonio, Texas
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Now, I found that my brake lights are not coming on properly... the third light comes on, but the main lights do not. Any Ideas? I see there are two switches on the brake pedal... could one be bad or are all the lights controlled by the same switch?
Posted on: 2011/5/6 14:06
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bogus Re: Brake lights...
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San Pedro, CA
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All lights by same switch, AFAIK.

Year?

I would check bulbs first... never know, coulda had an over load that blew out the 1157s.
Posted on: 2011/5/6 16:39
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Fredbird Re: Brake lights...
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San Antonio, Texas
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1991

Bulbs are good.

Hazards, which come off the same 20Amp circut are good...

Also, the turn signal works... However, that's a seperate 20 Amp circuit.

And from what I can tell, the third brake light is on the same brake pedal switch as the main brake lights.

I'm hesitant to jumping wires yet until I'm completely certain.

One switch has only two wires going into it... (one Pink one Purple (I think that's for the Transmission).

The other has two going into it and 3 more on a seperate connector going into it as well.

The one with 5 wires (Total) going into it is definately the one that controls the third brake light... just not sure if it should also be controlling the other lights. I would assume so, but not certain.

Attach file:



jpg  Brake Light Switch.jpg (1.55 KB)
4126_4dc42c1b7a147.jpg 110X83 px

jpg  2WireBrakeSwitch.jpg (1.38 KB)
4126_4dc42e3b9a3e1.jpg 110X83 px
Posted on: 2011/5/6 17:31
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bogus Re: Brake lights...
Grand Imperial Pooh-Bah
San Pedro, CA
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ok... the brake ligths and turnsignels and marker lights all share the same bulb, but not the same filiment within the bulb.

The 1157 has 2 bulbs in one.

My lovely wife is scanning the test flowchart from the helm manual - its a 1992, but I am betting it's identical.

I will update with that flow in a couple of minutes.
Posted on: 2011/5/6 19:09
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bogus Re: Brake lights...
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Check the attached PDF.

If I was a betting man, I would be checking grounds.

Also, if the sockets are bunged up, they will effect operation, too.

Attach file:


pdf Chart 6 Stoplamps Inoperative.pdf Size: 235.47 KB; Hits: 413
Posted on: 2011/5/6 19:19
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flyboy Re: Brake lights...
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Turn signals and brakes use the same bulb filament.
Posted on: 2011/5/6 20:04
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'91coupe, LT4Hotcam, some other stuff.
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captmike13 Re: Brake lights...
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one switch could also be to disable the cruise control when the brake is pressed.
Posted on: 2011/5/6 21:18
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Fredbird Re: Brake lights...
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San Antonio, Texas
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I am looking at the chart... I assume Term B is the middle wire on the 3 wire harness?

Also, how do I know what are CKT 140, 17, 150(G401), 20

I know I need to get a Shop Manual... Workin' on that... just got the car a month ago.
Posted on: 2011/5/6 22:53
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Jeffvette Re: Brake lights...
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Quote:

bogus wrote:
Check the attached PDF.

If I was a betting man, I would be checking grounds.

Also, if the sockets are bunged up, they will effect operation, too.



At least give the guy a chance by giving him the wire chart.
Posted on: 2011/5/7 5:48
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Jeffvette Re: Brake lights...
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Quote:

Fredbird wrote:
I am looking at the chart... I assume Term B is the middle wire on the 3 wire harness?

Also, how do I know what are CKT 140, 17, 150(G401), 20

I know I need to get a Shop Manual... Workin' on that... just got the car a month ago.


CKT 140 Orange wire. Power, goes to connector cavity B
CKT 17 White wire. Stop lamp feed to hazard, goes to connector cavity A
CKT 150(G401) Black wire, goes to ground(passenger side halo)
CKT 20 Light Blue wire. Feeds CHMSL and ABS, goes to connector cavity C
Posted on: 2011/5/7 5:54
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bogus Re: Brake lights...
Grand Imperial Pooh-Bah
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hm.... at least I gave up the flow chart...
Posted on: 2011/5/7 6:13
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Fredbird Re: Brake lights...
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San Antonio, Texas
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Not on CF,

Thank you for the explination of the circuts... That REALLY helps out.

Now the probing makes more sense.
Posted on: 2011/5/7 13:57
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Fredbird Re: Brake lights...
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San Antonio, Texas
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I've checked CKT 140 (Orange) and I'm getting 12V when grounding it. -So, Fuse Block (Source) to Switch is good

I've checked CKT 17 (White Wire) with the circuit closed(Pedal Depressed) and I'm getting 12V when grounding it. -So the Switch is good

I've checked CKT 20 (Light Blue) with the circuit closed (Pedal Depressed) and I'm getting 12V when grounding it. -So the Switch is good on that part too.

The reason the third brake light comes on is because CKT 20 controls ABS and the third Brake light.

CKT 17 on the other hand goes from the Brake Switch to the Hazard/Turn Signal Assembly.

Conclusion: Since I can turn on my Hazards and the lights respond properly (Which come off the same fuse) it seems my issue is the connection from the brake switch to the Hazard/Turn Signal Switch. (Now I just need to figure out how to access the connection and see if it's reparable or if I need to replace the assembly. If it needs to be replace... I've also got to figure out how to replace it.)

I will draw out my diagram soon and post it here for others who may ever experience these issues. (Diagram will be based on discussion here, What I've found in my car, and my Haynes book.)
Posted on: 2011/5/7 18:13
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Jeffvette Re: Brake lights...
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The switch assembly is the top right hand side of the steering column. It is buried with a bunch of connectors and wires. From my memory, it is the only set of stuff on the right hand side of the column.
Posted on: 2011/5/7 19:39
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Fredbird Re: Brake lights...
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San Antonio, Texas
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My dad sent me the wiring schematics of his 1986 Corvette and it seems to be basically the same as my 1991 with a few variances. I'm hoping to get lucky enough where I don't have to replace the switch because that will involve removing diabling the AirBag, removing the steering wheel etc... At least that's what I see in the Haynes Manual.

Looks like I can just check connector 104 Wire "P" connection (This is the connector that goes to the Turn/Hazrd switch). I think I saw that connector under the wheel last time I was under the dash. I will test the opposite side of that connector and see if I'm getting voltage with the pedal depressed If not, I will try to fix that connection.

Maybe we're on the home stretch...
Posted on: 2011/5/7 20:04
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Fredbird Re: Brake lights...
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I just checked and that connector is not accessable fromt he bottom. So I'll need to remove the Steering wheel I guess... How difficult is that? Hanynes has you disable the airbag, and then the steering wheel is off. It doesn't cover the removal at all... they kinda skipped that part.

Unless there is a better way to replace the switch? How big of a job am I looking at?
Posted on: 2011/5/7 20:22
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Jeffvette Re: Brake lights...
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It does require removal on the wheel and SIR Coil. It is a crap job.

Before you go to the trouble of doing this, check the connector on the column. It has about twelve wires going into it and is a long flat connector.
Posted on: 2011/5/7 20:26
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Fredbird Re: Brake lights...
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Is that accessable by removing the steering column bracket? I'm looking online right now and typically those connectors are in this lower area of the steering column.
Posted on: 2011/5/7 20:40
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Jeffvette Re: Brake lights...
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Removing the bracket may help give you some room. I'd have to crawl back under and see. Been a while since I played around with one.
Posted on: 2011/5/7 20:45
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Jeffvette Re: Brake lights...
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If you do need the new switch assem, it is part number 1995974. Dealer cost is 46.93 and retail is 93.86.
Posted on: 2011/5/7 20:49
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captmike13 Re: Brake lights...
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Another troubleshooting tip. If you step on the brake when the flashers are on they should stop, then continue flashing when the brake is released. At least this is how it is on my 85.
Posted on: 2011/5/7 21:03
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Fredbird Re: Brake lights...
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San Antonio, Texas
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I turned on the hazards and then hit the brake... They did not stop. So that still leads me to think switch is not getting power when I hit the brake. Hopefully the circuit didn't "Burn Out" on the switch. I know I had the hush panel off when I was adjusting the Hood release and when I drove it one day the panel was off... I'm thinking I might have kicked the wire and it could have pulled it loose.
Posted on: 2011/5/7 21:53
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Fredbird Re: Brake lights...
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San Antonio, Texas
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Found the wiring harness... looks like it's been repaired once before at that particular wire... didn't get to test it because it's mother's day. ;) maybe early in the morning. I'll submit a picture when I get back home so you guys can verify I am looking at the right wiring harness.
Posted on: 2011/5/8 23:09
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Jeffvette Re: Brake lights...
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Your car at some time may have had a euro brake light kit installed. This requires the white wire to be cut.
Posted on: 2011/5/9 1:17
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Fredbird Re: Brake lights...
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San Antonio, Texas
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I was able to test the connection this morning, and it was as I suspected... Right there at the connector. (Wire connection "P") When I pushed the wires together a bit tighter they lights came back on.

I will put in a bypass wire tonight so that I don't need to rely on the plastic connector and pins anymore. Maybe this winter I will replace the whole Turn Signal/Hazard mechanism. because I also need to replace my dimmer switch since it only works if the steering wheel is ALL the way in the Down position. I figure I'll already be there might as well take care of it all...
Posted on: 2011/5/9 15:40
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captmike13 Re: Brake lights...
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Glad ya found the problem.
Posted on: 2011/5/9 15:54
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bogus Re: Brake lights...
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If the dimmer is only working when the wheel is down, then there is an issue in the harness in the steering column, and I don't see the association, to be honest.

Get the FSM before you tackle the steering column!!! It's fiddly.

Also, consider getting new everything - turn signal, ignition, multifunction, tilt rebuild, everything. Take the wheel off, take the column out and do it right.
Posted on: 2011/5/9 16:30
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Fredbird Re: Brake lights...
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San Antonio, Texas
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I didn't think there would be any association between tilting the wheel and the dimmer switch, but that is what works. I read about someone else having that problem on "Another" forum and when they tilted theirs all the way down, it worked. My problem was, mine was stuck on "High" and wouldn't go off...

Don't know if it would be a good idea to spray some electronics cleaner in the cavity where the signal stem goes in... that may free the dimmer switch up just enough for the summer and then I can replace it over the winter.

Thoughts?
Posted on: 2011/5/9 18:29
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Fredbird Re: Brake lights...
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Here is the picture of the bad connection... You can't see it well in this picture, but the last connection (Connection "P" Last set of white wires on right) was the problem. When I pushed them together better it started working. I noticed that someone tried to solder the wire back in place right at the connector.

Attach file:



jpg  BadConnector.jpg (817.46 KB)
4126_4dc835ae7bc07.jpg 1836X1098 px
Posted on: 2011/5/9 18:42
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Jeffvette Re: Brake lights...
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That would be your problem.
Posted on: 2011/5/9 21:59
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joey91 Re: Brake lights...
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on my vette 1991 one switch drive the thirt light and second switch drive regular brake light, I make the test myself.
Posted on: 2011/6/19 2:19
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vette079 Re: Brake lights...
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Quote:

joey91 wrote:
on my vette 1991 one switch drive the thirt light and second switch drive regular brake light, I make the test myself.


And you are... Where in the world?
I´m also from outside the US, but maybe if you are outside the US and have different regulations regarding the brake lights.
If imported by a dealer, they may have changed it before selling it.

Netherlands, Germany, Sweden, pretty much all of Europe have the same rules for brake lights and they are a bit different from US rules.
Posted on: 2011/6/19 20:35
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