The Trombetta solenoid should solve your problem - probably "for good", as it did in my case. Note that this continuous duty solenoid is also rated for up to 600 amps of inrush current.
It's a bit larger than the stock one, so I had to do some fancy finger contortions and creative wire routing to fit it into the same space in the steel enclosed distribution box where Winnebago intents for it to be. So far it has just sat there doing it's thing year after year - it doesn't even make as loud a "thump" as the original one did when I turn the ignition key.
For what it's worth, I have a permanent four-place resolution voltmeter mounted on the dash in the cab that constantly shows the voltage on the coach's 12 volt system (monitors system voltage AFTER the coach battery disconnect switch). That's how I discovered that the alternator was not always getting hooked up to the coach batteries after starting the engine.
This voltmeter also tells me whether or not I remembered to turn the coach battery disconnect switch back ON, after gassing up, so our food in the refrig isn't warming up when going down the road.
