How to check 240v baseboard heater...without connecting supply wires and thermostat?
Put the ohm meter across the two wires from the heater and see if there is continuity. You might even be able to find out what the resistance should be by checking the manufactures sight. If not then watts divided by volts should give you a rough idea of what it should be.
If the last test checks out then you should test from each line to ground. It should be open with no connection.