Rectifiers

There is No Oil in the Rectifier.

There ARE capacitors in the rectifier that can spew a Corrosive Oily like Electrolyte when they fail, howerver.

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Your Random use of Red and Black wires for BOTH 12v Positive AND Ground connections is confusing and a bad practice.

Use RED for Power and Black for Grounds.

If forced to use Black for Power Cables, use extra-long sleeves of RED heat-shrink at the connections.

Keith,

sometimes the cable shoes are just not tight enough to make a reliable connection to the male rectifier connectors. Perhaps you want to check them and gently rework them where necessary to ensure a tight fit.
Also I have come across cases were one of the cable shoes did not click in the plastic housing correctly and, instead of being moved on it’s male connector, was pushed (backwards) slightly out of the plastic housing - again that is no good for a reliable and low resistance connection.

Peter