Siemens Thyristor SPNO 3RF23101AA02 shorted

[applecruncher1]

Hi,

We have a jacketed tank with a heating element (220 VAC, 650W) that is connected to a Siemens Thyristor SPNO 3RF23101AA02 as shown in the picture below. Our tank has a "Day", "Night", and "Off" options that can be controlled with a SP3T switch that determines whether to heat the tank to 45C, 31C, or no heating at all respectively. My problem is that the leads (1 and 2) of the Siemens Thryistor are normally closed even when its switch supply (A1 and A2) is not energized. Because of this, even when the SP3T is set to "Off" option, the heater is turned on.



This is how it looks like with the front cover removed:


Removing the pcb, I think underneath is some sort of a circuit inside a silicon gel. I tested the leads 1 and 2 and they are shorted. Sorry I do not know what I'm seeing below as I have a limited knowledge in electronics. Is this supposed to happen? The Siemens Thyristor is an NO contactor so there should no connection from Lead 1 to Lead 2 in the first place. What could be the cause of this?



Thanks,