I've installed many of these and they always worked fine. This time there is serious arcing at ground when the box blinks fast during ignition. It burned out my multimeter when checking voltage at 24 when set at 200 vac.. The box came with a blue line across the top of the damper control plug which makes me wonder if it's a return or a second. Also I notice the inside of the box will move up and down in the black plastic. Going to try another today. Also this conveyor pizza oven will ignite and run fine if I touch and hold the red meter lead on the 24 input terminal with black to ground set at 200vac.. The minute I take the meter lead off the terminal the burner will shut off. There is an arc from terminal to meter lead while doing this. Strange! There must be a high voltage bleed to the 24vac. Circuit in the box. Can't beat made in Mexico!!