This circuit come from a 2 speed fan (I think) control circuit from a wall heater. Picture attached. This circuit is use to control the fan force heat for a wall heater (there stop, slow, fast). I know the middle switch is a thermal switch (it close when the temperature reach 120 deg f) I know this from testing. In the top "switch" the black and red wire goes to the motor. This is about all I know

Can anyone help me understand the logic of this circuit. Can anyone generate a circuit diagram from the pic? I am thinking the bottom switch is another thermal switch. I am thinking the top switch is a relay that would switch the output for the black and red wires (output black for fast speed red for slow speed and non for stop). But all these are guess on my part.

thanks for your help in advance. Right now what is happening is the fan is switching on and off really quickly when heading up (I think what is happening is instead of switching to slow speed it turn off). But it would help with the trouble shooting to understand the circuit.

Also it would help if someone could point to a link or something like that so I can learn to read and understand thermal switch and relay destination (that is there is marking on the switch in the picture would be nice to be able to read it and figure out what it is suppose to be).

thank again

 

Photo of the other side?

 

here is the other side of the center thermal switch. There is no wiring on the other side. The other side is exposed to the hot gas of the firing chamber.