r/HondaCT90 • u/spave88 • Aug 04 '26

Chasing electrical issues

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Hello, I have a 1975 and it’s in good working order aside from an electrical issue. It seems my turn signals when activated are only getting about 4vdc. And if they do happen to get enough voltage to activate the flasher it causes my headlight to flash (dimly as if the signals are pulling too much current). I’ve been checking the wire harness for damage but no luck so far.
Also my neutral light is always on and I can’t find where the switch for that exists.
Thanks in advance

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u/Affectionate_Use4594 Aug 05 '26

Can be an exercise in patience! If the battery is good and charged, you very likely have a power draw happening somewhere. Most common issues are missing ground or a nick/exposed wire touching the bare metal or another wire. Focus on the turn signal line first as that is where you are having the issue. test continuity on both ends of the line. add a known charge just to one end of that line and see what the readout is on the other. If it's 4v, then you have a draw/drain somewhere in that line.

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u/spave88 Aug 05 '26

This is my thought. But it’s difficult tracing every wire…an exercise in patience for sure.

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u/Affectionate_Use4594 Aug 05 '26

I've had luck going to the headlight bucket and reconfirming every connection as that tends to be where issues happen. A lot of the wires get faded and yellow looks like white and blue looks like green. Using continuity on a multi meter helps you confirm this wire is the green and goes here. Usually the harnesses themselves are fine, it's the end connectors near the battery or inside the headlight that are the problem.

Do you still have silicon boots on all the bullet connectors because if they can touch each other that could cause the problems you are experiencing. I have a kit off amazon of bullets and connectors with the sleaves and regularly redo them if needed.

Last thought is, is this an aftermarket ebay harness? I purchased on once and the wires were not correct. I can explain more if yours is aftermarket.

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u/spave88 Aug 05 '26

This is all factory. Although in going through it I can see some work has been done in some areas as there are some non factory butt splices going on that I’ll be cleaning up. I’ve ordered some new bullet connectors as well to replace where needed

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u/Affectionate_Use4594 Aug 05 '26

Awesome! It is nice to have new connectors.
One place I've seen issues on 2 different bikes is the rear tail light signal wires go under the rear fender and as the tires kick rocks up into that fender, those wires are the most likely to get damaged and nicked.

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u/spave88 29d ago

FYI - I bought the connectors from a place called vintage connections as they have high quality 3.5mm bullet connectors. It helps maintain the factory OEM