I have been struggling with flickering lights for over a year but over last few months have become quite troublesome (more on that later). Searching the COG forums I found several threads on the pulsing or flicking light issue so it is not uncommon. There never seems to be a conclusion, you know a description of the root cause and the fix. Always lots of good suggestions of things to check but never closure. I offer my experience in the hope of helping others. Yes, this is my first ever post. I have been lurking for years and learned a lot. I finally feel I have something helpful to offer.
Background: 2004 C10, 36K miles. Flickering lights first noticed about a year ago and have been getting worse. Recently had intermittent stalling at idle, when it stalled it was as if the key had been turned off (no dash lights). Have to cycle the key off/on then restart. I no longer trusted my previously rock solid reliable bike. Sad. So I dug in studied the similar forum threads.
Initial Debug: I started by simply measuring the battery voltage while the bike was running (and lights flickering). DVM shows the voltage is all over the place oscillating between 13 and 16V. The flicker, the engine sound, the voltage are all oscillating (pulsing) to the same beat. Now this is a fairly serious over charging issue, a good running voltage measured at the battery should be a steady 14.3 to 14.6V. Following suggestions from other COG forum threads I checked he simple stuff, battery connections, alternator connections, alternator field winding, alternator stator windings, alternator diodes, etc.
First attempt at fixing: I blame the voltage regulator. I purchased an aftermarket regulator from Rick's Motorsport Electrics, Part number 30-502. Problem not fixed. Symptoms unchanged. Apparently Rick's Motorsport Electrics has precisely duplicated the Denso regulator. So I spent $75 on a part I didn't need. But a serious plug for Rick's Motorsport Electrics, they offer a good replacement alternative for less that half the OEM price if you need one.
More Debug: Knowing the regulator is not the problem, I now think the regulator may be seeing (sensing) a lower voltage thus causing it to output the very high voltage I see at the battery. Now, if you are still with me you probably want to open the schematic (https://cog.memberize.net/clubportal/clubdocs/1328/C10_WiringDiagram.pdf). I start to focus on the path from/to the regulator (alternator on the schematic) note the feedback path to the alternator goes through the ignition switch. I measure the voltage drop between the alternator brown wire and battery positive, with Key on engine off, expecting to find something close to 0V but find 300mV, Hmmmm, I wiggle the key now see about 1V. There's your problem! I start the engine, there are the pulsing lights, gentle twist the key left and I have steady lights. It is the ignition switch. Now my stalling also makes sense, the brown wire also drives the coil on the main relay. The voltage drop in the ignition switch was sometimes so high that the main relay would drop out.
The fix: There is a write up somewhere on here about rebuilding the switch but I decide to try a solvent flush first. I read on another thread there is no way to get solvent through the key hole to the electrical contacts. You need to get to the back of the ignition switch. So tank off, bars/risers off, cut a couple zip ties and find/disconnect the ignition connector, remove upper triple clamp/ignition switch assembly. Verify problem by measuring resistance between brown and white wires with key on, wiggle key, etc. Remove small security screw that holds the back cover on the ignition switch, remove cover. I used brake cleaner but proper contact cleaner would be better. Spray liberally, let it soak in work the key back on/off, spray some more. Let try for a few minutes then repeat the resistance measurements between brown and white wires with key on, if the cleaning worked, expect less than 1 ohm. Let the switch dry overnight with the back cover off and verify good contact again. Reassemble and enjoy your Concours again.
Background: 2004 C10, 36K miles. Flickering lights first noticed about a year ago and have been getting worse. Recently had intermittent stalling at idle, when it stalled it was as if the key had been turned off (no dash lights). Have to cycle the key off/on then restart. I no longer trusted my previously rock solid reliable bike. Sad. So I dug in studied the similar forum threads.
Initial Debug: I started by simply measuring the battery voltage while the bike was running (and lights flickering). DVM shows the voltage is all over the place oscillating between 13 and 16V. The flicker, the engine sound, the voltage are all oscillating (pulsing) to the same beat. Now this is a fairly serious over charging issue, a good running voltage measured at the battery should be a steady 14.3 to 14.6V. Following suggestions from other COG forum threads I checked he simple stuff, battery connections, alternator connections, alternator field winding, alternator stator windings, alternator diodes, etc.
First attempt at fixing: I blame the voltage regulator. I purchased an aftermarket regulator from Rick's Motorsport Electrics, Part number 30-502. Problem not fixed. Symptoms unchanged. Apparently Rick's Motorsport Electrics has precisely duplicated the Denso regulator. So I spent $75 on a part I didn't need. But a serious plug for Rick's Motorsport Electrics, they offer a good replacement alternative for less that half the OEM price if you need one.
More Debug: Knowing the regulator is not the problem, I now think the regulator may be seeing (sensing) a lower voltage thus causing it to output the very high voltage I see at the battery. Now, if you are still with me you probably want to open the schematic (https://cog.memberize.net/clubportal/clubdocs/1328/C10_WiringDiagram.pdf). I start to focus on the path from/to the regulator (alternator on the schematic) note the feedback path to the alternator goes through the ignition switch. I measure the voltage drop between the alternator brown wire and battery positive, with Key on engine off, expecting to find something close to 0V but find 300mV, Hmmmm, I wiggle the key now see about 1V. There's your problem! I start the engine, there are the pulsing lights, gentle twist the key left and I have steady lights. It is the ignition switch. Now my stalling also makes sense, the brown wire also drives the coil on the main relay. The voltage drop in the ignition switch was sometimes so high that the main relay would drop out.
The fix: There is a write up somewhere on here about rebuilding the switch but I decide to try a solvent flush first. I read on another thread there is no way to get solvent through the key hole to the electrical contacts. You need to get to the back of the ignition switch. So tank off, bars/risers off, cut a couple zip ties and find/disconnect the ignition connector, remove upper triple clamp/ignition switch assembly. Verify problem by measuring resistance between brown and white wires with key on, wiggle key, etc. Remove small security screw that holds the back cover on the ignition switch, remove cover. I used brake cleaner but proper contact cleaner would be better. Spray liberally, let it soak in work the key back on/off, spray some more. Let try for a few minutes then repeat the resistance measurements between brown and white wires with key on, if the cleaning worked, expect less than 1 ohm. Let the switch dry overnight with the back cover off and verify good contact again. Reassemble and enjoy your Concours again.
