PID Switch Problems

Hello.

For a project, I need to make 3 PID-controlled heaters that work simultaneously. I’m using an arduino and 3 SSRs to control it. I’ve attached a quick sketch of my circuit diagram.

I have problems with the switch. When it doesn’t blow off one of the wires, the heaters don’t heat up (as shown by the red line in the top graph, attached below).

The switch I’m using is a “4 position 3 heat switch type” of an old stove top. (Pic below, clearest reference here: http://www.macspares.co.za/index.php?main_page=product_info&products_id=4502 ).

How am I supposed to wire the switch? It has the same 4 knobs behind the switch, but I don’t really care for controlling it through a manual switch. Rather, I’d like it to control the heating elements with the arduino, and just have the switch as a safety measure.

Would it be easier to just get another easier switch (type)?

Thanks.

switch.jpg