Author |
Message |
Harfend
| Posted on Tuesday, October 24, 2017 - 04:52 pm: |
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Here is a weird one... I have a 01 S3 and recently the brake light will only light when the engine is revved up above 3k. No matter which lever, front or back is used. I have plenty of juice in the battery (13.2) and the alternator is throwing a charge at idle if 14.3 volts. The front switch works fine when tested and the bulbs are not cracked, or have rusty sockets. Headlight and tail light works fine. I know the rear light switch is pressure activated and I haven't flushed the brakes in a while but the front should work as that is a mechanical switch. This is not good as the brake light should come on while idle at a stop light.... Any thoughts are welcome! Thanks, HARFEND |
Sportyeric
| Posted on Tuesday, October 24, 2017 - 08:51 pm: |
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Grounds. Weird electrical happenings are always grounding issues, IMHO. Although it could still be a switch. Trouble shooting can be a bitch. I had an issue a couple of years back where the brakelight didn't light but wherever we checked with a tester-light, everything was fine. Turned out to be a bad rear brake switch but it would pass enough current to light the tester bulb but not a real bulb. Spent most a day before we figured that out. Come to think of it, the testing was complicated by the fact that I already knew the front brake switch didn't work. In your case, unlikely that both switches would be testing good but still bad at the same time. So grounding. |
Akbuell
| Posted on Wednesday, October 25, 2017 - 02:02 pm: |
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Since it seems the issue is RPM dependent, there is most likely a loose connection or almost broken through wire. If your wiring harness is anything like the one on my X-1, power goes from the harness to each individual switch. When the lever is pressed, current flows to a connector (output side, if you will) at the rear brake switch. Check the connectors and wiring at/from the rear switch to the bulb socket, and the bulb socket to ground. Hope this helps, Dave |
Harfend
| Posted on Wednesday, October 25, 2017 - 05:05 pm: |
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Thanks for your replies! I have inspected the wires at both switches and found them clean and intact. I tested the front switch with my multi meter and it was perfect. I did not test the rear switch but I will. The bulb sockets were also clean and well greased. I will check the ground at the battery again and any other grounds I can find and report back... |
Natexlh1000
| Posted on Thursday, October 26, 2017 - 09:45 am: |
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Measure the resistance between the bulb socket and the negative terminal of the battery. |
Oopezoo
| Posted on Thursday, October 26, 2017 - 10:02 am: |
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If you suspect grounding, you can also use a set of clip leads to jump the socket directly to the battery negative terminal and see if the problem goes away. Also, just out of curiosity, I would check your voltage at the socket.....at idle, and again above 3k RPM. It could be a high resistance connection somewhere that only allows enough current to flow when the motor RPM is up and that alternator is cranking higher current. Grounding issues can cause some weird crap to happen. Especially if its no a broken ground, but a loose, corroded, or almost broken connection. |
Harfend
| Posted on Tuesday, November 28, 2017 - 08:17 am: |
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Pleased to report problem solved! Turns out the brake light wire going into the brake light assembly had broken where the wire was crimped onto the spade connector. I replaced the connector and soldered the connection and the brake lights at the slightest touch again! Thanks for all the replies, HARFEND |
Harleyelf
| Posted on Tuesday, November 28, 2017 - 10:59 am: |
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Had the exact same issue ten years ago on my S3. |
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