Sea-Fire ESRS Mark V unit 24v

It would be a great help if you posted the wiring diagram.

Solenoids usually have 2 ways to fail. The valve gets stuck in one position or the coil shorts out.

Solenoids come is 2 basic configurations , normally open(N/O) & normally closed(N/C)

I would guess without seeing the wiring diagram your solenoid is N/C. It take power to hold it open,24 volts per your post. No power, it closes. So it can't just be disconnected.

So first check if you have 24 volts at the windings (magnetic coil) . Then set your meter to ohms and see if you have continuity through the coil. This is to check for a short in the windings.

It sounds like the solenoid for the SeaFire is operating. Without knowing whether it is normally open or closed it's hard to tell if it is operating correctly.

Call Seafire. Is there an over ride switch for the SeaFire?

Remove, clean, lube, replace and tighten down all the battery terminals.

I've got a 16 year old optima in my truck that did the same thing. When it vibrated it would lose contact. My marine generator experience is limited, but a lot of generators I've messed with over the years won't run without a battery. Battery is used to control the generators electronics so surges at start up and shutdown don't cause issues. Simpler generators this probably isn't an issue. Do you have another battery to swap in and test the system? I would probably just replace it, although I repaired the one in my truck by using epoxy to hold the terminal in place. Doing fine for 3 years, but I don't think I would do that in a boat. Only did it because I wondered how long a good battery could last, and I've had it since I was 15.

If the battery post is turning ,replace the battery. Even if the internal connection is not broken yet the battery will leak around the post unless its a dry cell battery.

A relay is nothing more than a magnetic electrical operated switch. Easy to bypass, with a couple wire nuts (unless it's a solid state relay) and as long as doing this does not affect the rest of the circuits. . There is a lot of different looking makes and models of relays than will work just fine. You just need to be sure it can handle the load and the coil voltage is the same.

I won't give specific electrical advice without seeing a wiring diagram and a picture of the relay.

One relay might be for the shutdown switch.