Brake light problem (please read this one)
Thread Starter
Pro
Joined: Mar 2004
Posts: 584
Likes: 0
From: Okemos MI
Brake light problem (please read this one)
This is a strange one 
It almost like the tail lights and the brake lights have changed jobs... or voltage anyway. My taillights function fine (come on when the brake pedal is pushed) but kind of dim. The turn signals function fine too, but also kind of dim. When I turn on the headlights (and taillights) for night driving the taillights are very bright, so bright that you cannot tell when the brakes or turn signals are activated.
Strange huh?
Now I have done many things to the Vette this winter ... one being transforming the automatic to a 4 speed, the dash was out the steering column was out too. one more strange thing is my tach acts flaky ( jumps around at low speed and never reaches higher RPM)
Before the winter I built a new tach filter and it seemed to work fine then.
is there something I could have plugged in backwards? Do I have a bad ground? a bad switch?
Where are the grounds anyway? any tips on trouble shooting this? Anyone got a good schemantic? mines pretty small print.
This is dangerous I almost got rear ended last night.
Can you help?
Thanks,
John
It almost like the tail lights and the brake lights have changed jobs... or voltage anyway. My taillights function fine (come on when the brake pedal is pushed) but kind of dim. The turn signals function fine too, but also kind of dim. When I turn on the headlights (and taillights) for night driving the taillights are very bright, so bright that you cannot tell when the brakes or turn signals are activated.
Strange huh?
Now I have done many things to the Vette this winter ... one being transforming the automatic to a 4 speed, the dash was out the steering column was out too. one more strange thing is my tach acts flaky ( jumps around at low speed and never reaches higher RPM)
Before the winter I built a new tach filter and it seemed to work fine then.
is there something I could have plugged in backwards? Do I have a bad ground? a bad switch?
Where are the grounds anyway? any tips on trouble shooting this? Anyone got a good schemantic? mines pretty small print.
This is dangerous I almost got rear ended last night.
Can you help?Thanks,
John
Burning Brakes
Joined: Dec 2004
Posts: 918
Likes: 5
From: Gainesville FL
I have found two things that caused this behavior on my '76:
1. Some kind of short in the turn signal switch wiring. The brake light leads go to the turn signal switch before heading to the tail lights, so problems here also affect the brake lights.
2. Tail light bulb inserted incorrectly into the socket, so that both silver bumps were in contact with one of the two contacts at the bottom.
In my case, I had both problems simultaneously, so tracking down the cause was a PITA.
1. Some kind of short in the turn signal switch wiring. The brake light leads go to the turn signal switch before heading to the tail lights, so problems here also affect the brake lights.
2. Tail light bulb inserted incorrectly into the socket, so that both silver bumps were in contact with one of the two contacts at the bottom.
In my case, I had both problems simultaneously, so tracking down the cause was a PITA.
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
You should go back to the plug at the steering column and look for a wire hooked up wrong. You can unplug at that location and apply 12V to each circuit to see if they are good from there back. You can check the output from the column and see if the correct voltages are there with each function.
Melting Slicks
Joined: Dec 2000
Posts: 3,407
Likes: 2
From: Carmichael CA
Sounds like a loose ground. Due to the vette being fiberglass, each lamp socket has to be grounded with an extra wire to the frame. The frame in turn must have a ground strap going to the starter and the battery ground is in that area as well...I believe the tranny bolt above the starter is used for the battery ground and frame strap. But, it could also be a ground wire going to the switches...either light switch or turn signal. Ground faults are very very difficult to trace. Sometimes the best way to fix them is to buy some new wire and add a ground. I had a 1970 Ford van once that I finally just scrapped the entire wiring and bought several spindles of wire and re-wired everything.
Thread Starter
Pro
Joined: Mar 2004
Posts: 584
Likes: 0
From: Okemos MI
Guys,
Thanks for the ideas.
I felt it may be a ground also so one of my questions was where are the grounds? I do remember hooking up what I thought was a very small ground wire to the trans bolt and thinking "whats this one for?" I will double check the grounds at the tailights too but this problem is with both lights. The steering columm plug won't be easy but sounds like a possability.
Anyone else have some suggestions what I can check?
Thanks
John
Thanks for the ideas.
I felt it may be a ground also so one of my questions was where are the grounds? I do remember hooking up what I thought was a very small ground wire to the trans bolt and thinking "whats this one for?" I will double check the grounds at the tailights too but this problem is with both lights. The steering columm plug won't be easy but sounds like a possability.
Anyone else have some suggestions what I can check?
Thanks
John
Melting Slicks
Joined: Nov 2001
Posts: 2,668
Likes: 43
From: Eastern US XX
Originally Posted by Lotus76
Guys,
Thanks for the ideas.
I felt it may be a ground also so one of my questions was where are the grounds? I do remember hooking up what I thought was a very small ground wire to the trans bolt and thinking "whats this one for?" I will double check the grounds at the tailights too but this problem is with both lights. The steering columm plug won't be easy but sounds like a possability.
Anyone else have some suggestions what I can check?
Thanks
John
Thanks for the ideas.
I felt it may be a ground also so one of my questions was where are the grounds? I do remember hooking up what I thought was a very small ground wire to the trans bolt and thinking "whats this one for?" I will double check the grounds at the tailights too but this problem is with both lights. The steering columm plug won't be easy but sounds like a possability.
Anyone else have some suggestions what I can check?
Thanks
John
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Drifting
Joined: Mar 2003
Posts: 1,608
Likes: 3
From: Canberra AUSTRALIA
St. Jude Donor '05-'06
I had a similar thing when I had the wrong bulbs. You have to make sure you have the twin circuit bulbs where they need to be.
Or one of the bulbs has shorted out the filament from the dim to bright filament?
Good Luck.
Or one of the bulbs has shorted out the filament from the dim to bright filament?
Good Luck.
Thread Starter
Pro
Joined: Mar 2004
Posts: 584
Likes: 0
From: Okemos MI
Its Fixed!
Originally Posted by Lotus76
This is a strange one
It almost like the tail lights and the brake lights have changed jobs... or voltage anyway. My taillights function fine (come on when the brake pedal is pushed) but kind of dim. The turn signals function fine too, but also kind of dim. When I turn on the headlights (and taillights) for night driving the taillights are very bright, so bright that you cannot tell when the brakes or turn signals are activated.
Strange huh?
Now I have done many things to the Vette this winter ... one being transforming the automatic to a 4 speed, the dash was out the steering column was out too. one more strange thing is my tach acts flaky ( jumps around at low speed and never reaches higher RPM)
Before the winter I built a new tach filter and it seemed to work fine then.
is there something I could have plugged in backwards? Do I have a bad ground? a bad switch?
Where are the grounds anyway? any tips on trouble shooting this? Anyone got a good schemantic? mines pretty small print.
This is dangerous I almost got rear ended last night. Can you help?
Thanks,
John
It almost like the tail lights and the brake lights have changed jobs... or voltage anyway. My taillights function fine (come on when the brake pedal is pushed) but kind of dim. The turn signals function fine too, but also kind of dim. When I turn on the headlights (and taillights) for night driving the taillights are very bright, so bright that you cannot tell when the brakes or turn signals are activated.
Strange huh?
Now I have done many things to the Vette this winter ... one being transforming the automatic to a 4 speed, the dash was out the steering column was out too. one more strange thing is my tach acts flaky ( jumps around at low speed and never reaches higher RPM)
Before the winter I built a new tach filter and it seemed to work fine then.
is there something I could have plugged in backwards? Do I have a bad ground? a bad switch?
Where are the grounds anyway? any tips on trouble shooting this? Anyone got a good schemantic? mines pretty small print.
This is dangerous I almost got rear ended last night.
Can you help?Thanks,
John
Well its fixed...
After a lot of studying of the schematics, tracing circuits, reseating plugs, adding grounds and inspecting sockets I discovered the problem...
Get this... The lamps where in the sockets backwards :o
I didn’t even know this was possible but it was. The 1157 lamp has two filaments and two contacts at the base of the lamp and uses the shell for ground. 1157 has two bayonets; one mid shell and one low on the shell. The socket has two slots for these to mount in than twist.
Foolproof right?
NOT! You can install the bulb wrong and the problem you get is the wrong signal sent to the wrong filament. Each filament has different lighting properties (one will be brighter)You know just when you think you know a little about Vettes they humble you to keep you straight
Thanks for all who responded to this thread.
John
Racer
Joined: Feb 2005
Posts: 373
Likes: 1
From: Bayonne NJ
Had the same exact problem with my vette when i first got it. There should be a ground underneath the rear bumper. Not sure exactly which wire but there really aren't many under there. I took it off of the ground point that it was on and bolted it directly to the frame and it worked fine.
Burning Brakes
Joined: May 2001
Posts: 988
Likes: 1
From: Dyersburg TN
Originally Posted by Lotus76
Well its fixed...
After a lot of studying of the schematics, tracing circuits, reseating plugs, adding grounds and inspecting sockets I discovered the problem...
Get this... The lamps where in the sockets backwards :o
I didn’t even know this was possible but it was. The 1157 lamp has two filaments and two contacts at the base of the lamp and uses the shell for ground. 1157 has two bayonets; one mid shell and one low on the shell. The socket has two slots for these to mount in than twist.
Foolproof right? NOT! You can install the bulb wrong and the problem you get is the wrong signal sent to the wrong filament. Each filament has different lighting properties (one will be brighter)
You know just when you think you know a little about Vettes they humble you to keep you straight
Thanks for all who responded to this thread.
John
After a lot of studying of the schematics, tracing circuits, reseating plugs, adding grounds and inspecting sockets I discovered the problem...
Get this... The lamps where in the sockets backwards :o
I didn’t even know this was possible but it was. The 1157 lamp has two filaments and two contacts at the base of the lamp and uses the shell for ground. 1157 has two bayonets; one mid shell and one low on the shell. The socket has two slots for these to mount in than twist.
Foolproof right?
NOT! You can install the bulb wrong and the problem you get is the wrong signal sent to the wrong filament. Each filament has different lighting properties (one will be brighter)You know just when you think you know a little about Vettes they humble you to keep you straight
Thanks for all who responded to this thread.
John
Glad you got rid of your bug john...
