This should be self explainatory for someone who knows what it is.
How do I know if the selenoid looking thing towards the bottom right is working in this application?
Carl, This is your battery isolator. The Solenoid looks to be corroded but may still be working. If It was Me I would replace it now, not when you have to.
On lower left is a relay, probably the AC compressoer relay. These are cheap and I carry two of them as insurance.
Looks like all the cable and wire connections could use a good bit of cleaning up.
To verify solenoid op, use a Volmeter, should have voltage both sides when engaged.
Gary B
Carl, Now that I look at this photo Twice I wonder what the two wires that are on the left go to ? It LOOKS like this is where another solenoid was mounted and someone has screwed them down to the mounting plate.
Should ( or usually is ) be two solenoids, one is start solenoid and the other is boost.
Gary B
Gary is correct. That large rectangular box with heat sinks is the diode-based battery isolator.
Guessing, but probably center lug to alternator and the two outer lugs to chassis and house battery.
Brett
Carl, Took a THIRD look at that isolator, looks like the two wires in the lower left are attached to a SELF RESETTING Circuit Breaker. Would have to get a closer look to be sure, at any rate the connections could use some cleaning up. This is in an awkward position but one way is to remove one wire at a time and using plumbers tape ( emery paper ), clean each connection, use a wire brush on the posts, and replace each one as you clean it up. Some dieelectric Grease would not hurt either.
Gary B
Nice! Thanks Gary. I'm going to get right after ALL the connections on this and everything else right after the 4th.