3 out of 4 signals not working - 1980 GSX400

[Guest]

Three out of the four turn signals on my 1980 GSX400 just stopped working. The only one that works is the back-right signal. The turn signal indicator on the cluster only works when the switch to the left position. All other electrical seems to be working fine. Now because it's the rear right signal and the indictor for the left signal that works, I can't seem to wrap my head around where the problem could be. Any tips on how to troubleshoot this one?

gs400wiring.jpg

[Nessism]

How's the battery charge? The signals won't flash without a well charged battery.

[Oldspooneye]

How's the battery charge? The signals won't flash without a well charged battery.

Battery is fully charged and in great shape. I replaced it a couple weeks ago.

[mnferwerda]

You can swap bulbs just to rule out some freak event of 3 bulbs going bad at the same time.

[Oldspooneye]

Holy crap, I'm such an idiot. That's what it was. What are the odds of all three going at once? I hope that isn't just a symptom of a larger electrical problem. I'm not sure if that explains why the indicator on the cluster only works half the time. I can't get replacements until tomorrow so we'll see...

[Steve]

While you are playing with electrics, take a few moments and check the output of your charging system.

There are not many things that will cause three bulbs to fail at the same time, but over-voltage is one of them.

Just a quick, simple test will tell.
1. Connect your voltmeter to the battery.
2. Check voltage before turning the key ON.
3. Check voltage with key ON and engine OFF.
4. Start engine, check voltage at idle.
5. Slowly raise engine speed, noting voltage rise.
6. Check voltage at a steady 5000 RPM.

Let us know the results.

.

[Oldspooneye]

Check voltage before turning the key ON. - 12.7
Check voltage with key ON and engine OFF. - 11.85
Start engine, check voltage at idle - 12.5
Slowly raise engine speed, noting voltage rise. - 13
Check voltage at a steady 5000 RPM. - 12.85

Does that sound about right or is something off?

[Steve]

Voltage at 5000 should be much closer to 14. Your numbers show that you are starting with a decently-charged battery, but it is dipping below 12 with the key ON and the engine not running. The fact that it comes back up a bit when the engine is running is encouraging, but it should be considerably higher. This is showing that you might have poor connections or a dead leg on the stator.

Time to run more tests on the electrical system.

.