In the process of troubleshooting a battery charging problem in my 2009 B31, I ran into a mystery relay and some loose wires. I think they are unrelated to the charging problem, but I’m curious what they are.
There’s a green 12V 25 amp relay wire-tied to the coolant hose on near the alternator. The coil has a red wire that appears to be spliced to the red wire from the alternator, and a yellow wire that appears to go to ground. The switch had a poorly crimped (as in comes loose when you look at it funny) pair of wires to ground on one side and an empty uncrimped crimp-on connector on the other side.
However, we discovered a loose harness in the engine compartment. It is two wires in a flex conduit. Both wires are terminated in diodes (negative ends). The diode leads look like they might have been crimped together, and might have at some time in distant history been stuck together in the uncrimped connector. The flex-conduit runs to port near the battery charger. I _think_ it terminates into something that looks like another relay.
My theory is that (assuming the diodes were really supposed to be attached to the relay) that when the alternator is live, the relay would have grounded that cable. Maybe that’s a control signal for something else. So, just guessing—could this have something to do with a windlass relay? (I don’t have a windlass). Something else?
Pictures of the relay and 2 loose yellow wires (with the failed connectors removed) and the diode-typed cables attached: