88 Carrera. Brake lights......again.

[Junkbone]

I've had some issues with the brake lights for as long as I've owned the car. First fix was the two prong switches on the M/C. I was able to determine that problem by just jumping those wires to see if I had lights then. I did. Replaced switches. After a couple of days driving it blew the fuse#5 slot in the fuse panel. I replaced the fuse and all has been well up until now. All fuses are good but now I can't get lights by jumping the M/C switches. All three brake lights are out, bulbs are good. Maybe a common ground issue across all three lights? Seems as though they would be individually grounded though. idk. Any suggestions? Thanks

[DRACO A5OG]

Re-check the fuse. It may look good but it could be loose and losing continuity.

So you verified no power to the brake light with a volt meter, correct?

Check if there is power to the fuse as well.

When you replaced the Brake Light Switches, were they an aftermarket or Porsche brand? I find the Porsche brand to hold up better in a good system.

I write good because the the brake light assembly is the last thing you need to look at to insure the socket assembly is not compromised i.e. cracked, or fractured and shorting out. You see the socket assembly is held together by a PCB board type material and very brittle, expecially with all the years of pushing in the replacement brake lights or the not so good advice of pulling on the contact to make a better contact.



Here a member and I have rebuilt the PCB area with plastic. You can also re-press the crimps in front and rear of the socket. I went further to squeeze the socket for a tighter fit of the plug. I use Honda Light Bulbs as recommended by Daniel Stern. they are nickel finished to prevent corrosion. They also happen to be higher in wattage.

[geoz]

From what I experienced probably the main cause of the issues - not counting the age of the components - is the current going through the system.

I have previously installed a relay to ensure the BLS is no longer exposed to the high currents and that has definitely prevented arcing. I have also now installed LED brake light replacements to hopefully further lower the current through the system and I think they also turn on quicker than the old bulbs, however, now my cruise control is playing up. I may have to go back to the incandescent bulbs but did not have a chance to try that yet.

[Junkbone]

Thank you both. I have not checked for current at the bulb, but only because it was so unusual for all three to go out at once I assumed it would be at the M/C again. Fuse is intact. Common sense tells me that the switch at the M/C should have constant voltage and the switch closes with pressure from the system to complete the circuit. I have current to the brake light switches, but no lights even when jumping. I was really hoping you guys were gonna say "Oh, thats the hidden fuse under the back seat.' or, "Did you hit the reset button under the steering column" Haha. I will check a little better at the bulb housing but I'm starting to worry I may have a short somewhere. Is this a reasonable train of thought?

[A horse with no name]

Originally Posted by geoz

From what I experienced probably the main cause of the issues - not counting the age of the components - is the current going through the system.

I have previously installed a relay to ensure the BLS is no longer exposed to the high currents and that has definitely prevented arcing. I have also now installed LED brake light replacements to hopefully further lower the current through the system and I think they also turn on quicker than the old bulbs, however, now my cruise control is playing up. I may have to go back to the incandescent bulbs but did not have a chance to try that yet.

Hi, I also have replaced the brake and tail lights with LED's from 'Spoke' that are excellent. (24 LED's per side) A few others on this board are experiencing a similar problem. The LED board for the tail lights will remain on all though very dim. When disconnecting the Cruise plug all is well. 'Spoke' is close to working out the size of a resistor that will correct this issue.
If they are not his LED's, he may be able to help you with what size a resistor you should have.He is currently working out the resistor size for his LED set up's. Drop him a PM. To find him, just make a search for 'Spoke' and either his name or a thread with LED's will provide you with his address. He's a very nice guy, and as stated, his products are excellent in every way. BTW, if you replace only one side with a regular 1157 bulb you will find that your cruise will work. It appears that there is a leakage between the brake/tail lights and the Cruise wiring.

I hope that this is of some help to you.

[DRACO A5OG]

Originally Posted by Junkbone

Thank you both. I have not checked for current at the bulb, but only because it was so unusual for all three to go out at once I assumed it would be at the M/C again. Fuse is intact. Common sense tells me that the switch at the M/C should have constant voltage and the switch closes with pressure from the system to complete the circuit. I have current to the brake light switches, but no lights even when jumping. I was really hoping you guys were gonna say "Oh, thats the hidden fuse under the back seat.' or, "Did you hit the reset button under the steering column" Haha. I will check a little better at the bulb housing but I'm starting to worry I may have a short somewhere. Is this a reasonable train of thought?

Yes, reasonable. but will be verified by voltage test at the tail light assembly. Could be as simple as a dirty ground at the passenger side ground point behind the light assembly mount. That area is in a very harsh environment, sees allot of dirt and moisture. You will know what I mean when you remove it.