Somewhere around 11.5 for good ignition.
Check the igntitor to insure it is about 1/8 inch from ground.
Earth ground is not necessarey for the 12 volt DC system. Good connection between the battery negative and the rig's frame is necessary.
Disconnect the battery, use Ohmmeter between the disconnected wire and the battery terminal. With everything shut off there should be no reading, as in zero ohms.
How does the refer work when connected to shore power or genset? If works OK, then batteries! Refer should be manual set to propane for this test and not auto!
