You are measuring ripple. Which is residual AC after going through rectifier. Basically a function of how effective rectifier is converting AC to DC. It's very low, so rectifier is working well.
What you've done is measured resistance end-to-end of wires and then measured the voltage-drop across that distance. Let's measure resistance of individual wires without anything connected. Disconnect:
- both battery terminals
- plug from stator
- both plugs from R&R
Measure resistance:
- between + and - battery cable lugs (don't touch battery), should be
open-circuit/infinite ohms
- between each yellow-wire terminal at stator connector to other end at R&R connector
- between white +output wire at R&R to + battery cable
- between black/yel ground wire at R&R to - battery cable
- between black/yel ground wire at R&R to - chassis ground.
These last 4 tests should all be
zero ohms.
Look carefully at terminals inside each connector. They can get overheated and burnt over time due to corrosion. The wiring may test with zero-ohms between ends. But getting across these connectors with two burnt terminals increases resistance and you lose power on way to battery. At idle, there's little current flowing, so voltage-drop is small. At higher-revs, there's more current flowing, voltage-drop will be higher. V=IR
