Mechanic in the house?
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Hmmmm... It's been a while, but, 1. It's nearly 20 years old, and they didn't have all the electronic, computer-controlled whizbangs in them that make real diagnosis impossible. 2. It's intermittent. 3. It drains the battery overnight, which a single bulb should not do. Ergo: It's in the wiring harness, and probably involves more than one wire. I'd guess that abrasion has worn off the insulation on a couple of wires where the tail light harness makes a sharp bend around a metallic chassis component, but that's only a starting point. Some automotive wiring uses the quaint notion of wiring the hot side (positive) to each device and switching the negative to ground to turn them on. This causes some interesting sneak paths for current when something goes wrong. 1. Start at the brakelight; open it up and make note of the color of each of the wires. Expose the wiring from back to front as you work your way forward to the fuse block and visually inspect the wires for damage, especially where they go around corners or pass through a hinge, such as the trunk lid. Be prepared to spend all day at it, though, as getting to the harness isn't easy. or 2. Connect a time domain reflectometer at the bulb socket and ping each wire separately. Calculate the distance from the socket to the first discontinuity for each wire. Measure the shortest distance of the two and expose the cable at that distance from the socket and repair the damage. Simple... :) It would be great if you could arrange to do the search while the light is on, but Murphy's Law assures that you won't get that lucky. Good luck! :-D
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
A better answer would be to take it to a mechanic and let them deal with it. :)
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
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"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001 -
Actually, when I reconnected the battery a couple weeks ago, I thought I would check and found that the brake light was lit on the passenger's side with the car off. I tapped the brake pedal and looked again without starting the car or turning the ignition on and the light went out. I would think the switch would be the most suspect but to me I would think it would enable both of them not just one. It is about time to drive another car under that radiator cap ;)
Rocky <>< Recent Blog Post: Silverlight Domain Names up for grabs! Thinking about Silverlight? www.SilverlightCity.com
I have an old Jeep Cherokee that will do the same thing on occasion. There is normally a spring on the brake pedal that returns the pedal to the "normal" position pulling the pedal up into the nonbraking position. In my case the spring was old and tired and allowed the pedal to sag slightly making the switch. All that I did was made sure to lift the pedal slightly with my foot when I exited the vehicle...... sounds silly but saved me the hassle of trying to climb under the dashboard and try to replace some spring. I would suggest applying the brake pedal while the car is in park and then letting off. Check the light to see if it is lit, then try lifting the pedal with your foot and verify the light goes off. If that fixes the problem, you can check to see if the switch position can be adjusted, replace the spring, or teach them to lift the brake pedal. You may have to try quite a few times to get the pedal to sag enough to make the switch.... it sounds like an intermittent problem.
Uptight Ex-Military Republican married to a Commie Lib - How weird is that?
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Hmmmm... It's been a while, but, 1. It's nearly 20 years old, and they didn't have all the electronic, computer-controlled whizbangs in them that make real diagnosis impossible. 2. It's intermittent. 3. It drains the battery overnight, which a single bulb should not do. Ergo: It's in the wiring harness, and probably involves more than one wire. I'd guess that abrasion has worn off the insulation on a couple of wires where the tail light harness makes a sharp bend around a metallic chassis component, but that's only a starting point. Some automotive wiring uses the quaint notion of wiring the hot side (positive) to each device and switching the negative to ground to turn them on. This causes some interesting sneak paths for current when something goes wrong. 1. Start at the brakelight; open it up and make note of the color of each of the wires. Expose the wiring from back to front as you work your way forward to the fuse block and visually inspect the wires for damage, especially where they go around corners or pass through a hinge, such as the trunk lid. Be prepared to spend all day at it, though, as getting to the harness isn't easy. or 2. Connect a time domain reflectometer at the bulb socket and ping each wire separately. Calculate the distance from the socket to the first discontinuity for each wire. Measure the shortest distance of the two and expose the cable at that distance from the socket and repair the damage. Simple... :) It would be great if you could arrange to do the search while the light is on, but Murphy's Law assures that you won't get that lucky. Good luck! :-D
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
You need a transmission line plus the dieletric constant to calculate the propagation speed otherwise you will look in the wrong place for the break, it could even be the unterminated end. Oh, plus the characteristic impedance or you could get a launch reflection. Moi? Difficult? :rolleyes:
Visit http://www.notreadytogiveup.com/[^] and do something special today.
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It is? :confused:
I found it funny :)
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Do you work for Microsoft? :)
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
No, but I am enslaved by them.
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I have an old Jeep Cherokee that will do the same thing on occasion. There is normally a spring on the brake pedal that returns the pedal to the "normal" position pulling the pedal up into the nonbraking position. In my case the spring was old and tired and allowed the pedal to sag slightly making the switch. All that I did was made sure to lift the pedal slightly with my foot when I exited the vehicle...... sounds silly but saved me the hassle of trying to climb under the dashboard and try to replace some spring. I would suggest applying the brake pedal while the car is in park and then letting off. Check the light to see if it is lit, then try lifting the pedal with your foot and verify the light goes off. If that fixes the problem, you can check to see if the switch position can be adjusted, replace the spring, or teach them to lift the brake pedal. You may have to try quite a few times to get the pedal to sag enough to make the switch.... it sounds like an intermittent problem.
Uptight Ex-Military Republican married to a Commie Lib - How weird is that?
Actually, I checked today. The light was on again when I connected the battery, so I lifted the pedal and it was still on. Only when I pressed the pedal enough to kick both lights on did it finally go out when released. After awhile, the light comes back on again on that one side. Almost to the point to just run a flip switch on that brake light and have it triggered when the ignition comes on :)
Rocky <>< Recent Blog Post: Silverlight Domain Names up for grabs! Thinking about Silverlight? www.SilverlightCity.com
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A better answer would be to take it to a mechanic and let them deal with it. :)
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
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"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001Isn't that a lot like handing someone your credit card and after they ring it up, you ask "How much will that be?" :)
Rocky <>< Recent Blog Post: Silverlight Domain Names up for grabs! Thinking about Silverlight? www.SilverlightCity.com
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My mother's Cadillac (early 90's) has a tail or brake light that likes to come on while the car is parked and drains the battery completely overnight. It can go days without happen, then presto, the batter is dead. Found out once when someone called and said the tail light was on and found that just the right side tail light (or brake like don't remember which) would come on for no known reason. Anyone heard of such a thing? The lights all work like normal, but this one light likes to come on at will when the car is off and parked. She cannot really be connecting and disconnecting the battery every time she uses the car, but do not want to take it in and see a huge bill without any results. Any ideas?
Rocky <>< Recent Blog Post: Silverlight Domain Names up for grabs! Thinking about Silverlight? www.SilverlightCity.com
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My mother's Cadillac (early 90's) has a tail or brake light that likes to come on while the car is parked and drains the battery completely overnight. It can go days without happen, then presto, the batter is dead. Found out once when someone called and said the tail light was on and found that just the right side tail light (or brake like don't remember which) would come on for no known reason. Anyone heard of such a thing? The lights all work like normal, but this one light likes to come on at will when the car is off and parked. She cannot really be connecting and disconnecting the battery every time she uses the car, but do not want to take it in and see a huge bill without any results. Any ideas?
Rocky <>< Recent Blog Post: Silverlight Domain Names up for grabs! Thinking about Silverlight? www.SilverlightCity.com
I'll work backward; many cars (most?) have a brake/transmission interlock. You cannot put the car into gear unless the brake pedal is pressed. The relay for this is often connected to the brake light. When this relay goes bad, you can't put the car into gear. What if this relay can go bad in a different way? Thus it may not be total chance, but rather how the car was put into park.
Anyone who thinks he has a better idea of what's good for people than people do is a swine. - P.J. O'Rourke
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My mother's Cadillac (early 90's) has a tail or brake light that likes to come on while the car is parked and drains the battery completely overnight. It can go days without happen, then presto, the batter is dead. Found out once when someone called and said the tail light was on and found that just the right side tail light (or brake like don't remember which) would come on for no known reason. Anyone heard of such a thing? The lights all work like normal, but this one light likes to come on at will when the car is off and parked. She cannot really be connecting and disconnecting the battery every time she uses the car, but do not want to take it in and see a huge bill without any results. Any ideas?
Rocky <>< Recent Blog Post: Silverlight Domain Names up for grabs! Thinking about Silverlight? www.SilverlightCity.com
You might try checking the brake light switch, I had one fail one time that would do exactly what you are saying. It was a partial short, and would drain the battery with no apparent light coming from the rear lamps. Changing the switch solved the problem, finding it involved pulling the plug off the switch mounted on the master cylinder, and seeing the meter needle go to zero. The brake and rear lights make the return circuit through the metal frame of the vehicle, with the voltage being supplied throught the wires routed to them through the body, after going through the switches, meters, fuses, etc. You can buy a haynes manual with a wiring diagram from an auto parts store that will show you how everything is routed, etc. Good luck
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Actually, when I reconnected the battery a couple weeks ago, I thought I would check and found that the brake light was lit on the passenger's side with the car off. I tapped the brake pedal and looked again without starting the car or turning the ignition on and the light went out. I would think the switch would be the most suspect but to me I would think it would enable both of them not just one. It is about time to drive another car under that radiator cap ;)
Rocky <>< Recent Blog Post: Silverlight Domain Names up for grabs! Thinking about Silverlight? www.SilverlightCity.com
It's a long shot, I know, and I wouldn't expect even a US car maker could be so dumb, but might they have terminated both brake lights at the switch? If so, a loose connection at the switch could cause the problem in one light, but not the other. If only one wire is terminated at the switch there's no way the switch could be at fault.
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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My mother's Cadillac (early 90's) has a tail or brake light that likes to come on while the car is parked and drains the battery completely overnight. It can go days without happen, then presto, the batter is dead. Found out once when someone called and said the tail light was on and found that just the right side tail light (or brake like don't remember which) would come on for no known reason. Anyone heard of such a thing? The lights all work like normal, but this one light likes to come on at will when the car is off and parked. She cannot really be connecting and disconnecting the battery every time she uses the car, but do not want to take it in and see a huge bill without any results. Any ideas?
Rocky <>< Recent Blog Post: Silverlight Domain Names up for grabs! Thinking about Silverlight? www.SilverlightCity.com
I do know that European cars have an additional "Park" lock. You have to twist the ignition anticlockwise twice to operate this mode and this leaves the parking lights on. So if you just want to switch off, you only turn the ignition anticlockwise once.
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Isn't that a lot like handing someone your credit card and after they ring it up, you ask "How much will that be?" :)
Rocky <>< Recent Blog Post: Silverlight Domain Names up for grabs! Thinking about Silverlight? www.SilverlightCity.com
In the US, they can't start work unless you sign an estimate for parts and labor.
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
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"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001 -
My mother's Cadillac (early 90's) has a tail or brake light that likes to come on while the car is parked and drains the battery completely overnight. It can go days without happen, then presto, the batter is dead. Found out once when someone called and said the tail light was on and found that just the right side tail light (or brake like don't remember which) would come on for no known reason. Anyone heard of such a thing? The lights all work like normal, but this one light likes to come on at will when the car is off and parked. She cannot really be connecting and disconnecting the battery every time she uses the car, but do not want to take it in and see a huge bill without any results. Any ideas?
Rocky <>< Recent Blog Post: Silverlight Domain Names up for grabs! Thinking about Silverlight? www.SilverlightCity.com
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You need a transmission line plus the dieletric constant to calculate the propagation speed otherwise you will look in the wrong place for the break, it could even be the unterminated end. Oh, plus the characteristic impedance or you could get a launch reflection. Moi? Difficult? :rolleyes:
Visit http://www.notreadytogiveup.com/[^] and do something special today.
Isn't that information in your owners manual? :-D In practice, you can measure the other side as a baseline, assume it's about 6' shorter (assuming the fuse block is under the driver's side of the dashboard, and calculate a fair estimate. Better to know that it's somewhere near the passenger door than to rip out the entire cable. Once you know the propagation velocity, it's easy to simply ignore the launch reflection, much as a radar system uses a range gate to ignore reflections that are too close to be real. The greater challenge will be to decide which blip is a short, and which is just a bend in the cable. A network analyzer might also be helpful, but I never liked s-parameters much. I like math, but not that much! ;)
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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:laugh:
Rocky <>< Recent Blog Post: Silverlight Domain Names up for grabs! Thinking about Silverlight? www.SilverlightCity.com
