11/3/4 volts is very nearly a dead battery. Don't know about water heaters but most refrigerators will now work if voltage is much less than 11 volts because the thermostat can't properly operate. I'd check your converter and/or your battery to find out why dc voltage is so low.
Good luck / Skip
2011 F-150 HD Ecoboost 3.5 V6. 2550 payload, 17,100 GCVWR -
2004 F-150 HD (Traded after 80,000 towing miles)
2007 Rockwood 8314SS 34' travel trailer
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