This one is a bit unclear on reflection. There was a buzz when I tested for continuity on a plugged in unit so looking good here as well. But it's just backplate and wires I am testing. If I put a unit into back plate there's no way to testOn reflection, you may have to have the whole T4 unit assembled (with batteries). So remove it and connect two bits of wire to terminals A & B, reassemble it, turn up the heat setting to get the flame signal on and test for continuity (o) with the M.meter connected between the two wires, turn the setting down to check that the contacts open, M.meter reading 1.