4E uses 12V DC to BOTH switches.....
Electric On/Off switch sends 12V DC to the circuit board which then uses the DC to trigger a DC Relay that allows 120V AC to the element
So the DC to the propane on/off switch can be jumpered to the electric on/off switch
White wire from electric switch to circuit board
Orange wire from propane switch to circuit board
The 120V AC that went to electric switch in 3E version should go to the DC Relay AC Input wire.output wire to element
Current 120V AC Circuit Breaker still used
See pgs 23,24,25 in this manual