Bill,
As best I know, both sides of the Solenoid switch contacts will be hot (one cable goes to the positive terminal of the Chassis battery and the other cable to the positive terminal of the House batteries). When the solenoid actuates (closes), it parallels the positive terminals of the Chassis and House batteries. The negative terminals of the batteries are connected directly to the Chassis, which is a common ground.
The dash switch, on the other hand, will have only one hot side (usually from the House batteries) when in it’s normal position. The cold side of the dash switch goes to the coil of the Solenoid switch and will actuate (close) the Solenoid switch when the dash switch is closed, paralleling the Chassis and House batteries.
Note: when using jumpers, most people connect them to the terminals of the battery, not the battery posts themselves. This method, in fact, simply bypasses the “dead” battery with the battery used for jumping. It does nothing to prove the terminals are secure.
If it were I, before doing anything else, I'd check the connections to the Chassis battery, especially the Negative terminal. If the terminals are not truly secure, using the "E" start switch will not help much. If this proves true, there's a very good chance the Chassis battery is not be getting a complete charge.
Suggestion: the next time this happens, open the hood and twist the connections while pushing them down hard. Then first try to start it just using the Chassis battery. If the Chassis battery won't do it alone, then try using the "E" start switch to bring the House batteries on line.
Let us know what happens.
