Pamco ignition causing 1VDC voltage drop

AJA

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Hello, I have a 1979 XS400 with a dim headlight because the wires for the headlight only outputs ~11VDC. I traced the wires from the battery and found that everything past the main fuse has a voltage drop (~1VDC drop). If I disconnect the red wires from the PAMCO ignition, it eliminates the voltage drop.

I noticed during my troubleshooting that the (stock) coils get warm/hot when the ignition is on (engine not running), which also seems odd. I have tried disconnecting the red coil wires, but it does not change the voltage. The other wires on the PAMCO also don’t affect the voltage… only disconnecting the red wires.

I also have had a problem where my battery drains on long rides which causes the bike to die. I had always thought this was the headlight that drained the battery, but I suspect that the two issues are related.

Full disclosure, I have eliminated the headlight cutout relay, and turn signal cancelling unit when I built the bike, but the fact that everything goes back to normal voltage as soon as I disconnect the red wires from the PAMCO Ignition tells me that the PAMCO is causing the issue.

I have attached a modified wiring schematic showing my modifications, as well as the PAMCO ignition hookup.

Looking for some advice on how to fix the issue. Any advice is appreciated.
XS400 Modified Schematic.jpg
XS400.jpg
 
Check your fuse box for corrosion, check any grounds as well. It sounds as if the circuit is experiencing a lot of resistance.
 
Thanks for the the reply.

I don't think that the ground is the issue because I took ground directly from the battery when testing the voltage and still saw the same drop.

The fuses aren't ideal, but they're not too bad. Plus, if the fuses were the issue, shouldn't I see a voltage drop across them?

I also checked and the stator is working properly... battery voltage is 13.3v with the bike off, 14.5v running at ~3000-4000 rpm (I don't have a tachometer).
 
My XS360 had a pretty significant voltage drop with the ignition coils sucking power.

There can be a significant voltage drop through the ignition switch. Some owners of older bikes do a mod adding a relay straight off the battery that supplies the ignition system. The ignition switch activates only the relay instead of carrying the full current for a longer distance.
 
Thanks. I checked the ignition as well. It has the same voltage in as out.

I also thought about using a relay to wire my headlights directly off the battery. It would make my headlight brighter, but I'd prefer to fix the issue causing it.
 
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