170T will not kick on when I plug it in and turn the switch on. I have power the the switch and the thermostat but no power past the board.

Question edited for maker name.

Troubleshooting videos

https://www.google.com/search?q=reddy+heater+170t+will+not+start

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Check for a "reset" button.... fairly close to where the 110 power comes in.

Yeah i would change out that board .Should be a 3 amp fuse so maybe as simple as that but if not a cycling blower motor is a tell tale sign of curcuit board

The photo eye needs cleaning,the eye is not reading,I would send you a pdf manual but I can not on here there is no place to send it to you sorry

the thermostat sends a signal to the circuit board. Not knowing anymore than I do about your heater or furnace I would suggest that that is a good place to start. Any limit or safety switch wouldnt coincidentally shut off the heater when it reached the set temp.

If you can remove cabinet, check glass fuse on power supply board.

After that it is probably the power supply board or the control board - see a service department

What kind of a unit is it? Is it integrated with a furnace in the attic? Need to now this information. Also, turn the thermostat to Cool/Auto and go outside to see if the condenser unit is running, if so, then there is a problem with the indoor blower motor or thermostat. Jumper the green and red wires on the thermostat and see if the blower comes on. If so, you have a bad thermostat. If not, you could have a bad fan motor or capacitor.

The thermostat is the controller.

Are the ignitors intact? In other words, does the element make a loop back to the ceramic portion. The purpose of the LED is to notify the user of a defective ignitor. The other possibility is a bad control board.

If the ignitor is intact, but no power coming from the board (ignitor only glows for 5 seconds), then the board is bad or the fuse is blown. You might want to test the photocell while you are at it.

You will need to locate the correct model numbers to order the correct parts. "170T" & "125T" are only part of the correct model designation.

Post back if you have further questions.

You may have a low pressure or high pressure switch tripping out the board as well. You might try cleaning both the indoor (evaporator) coil and the outdoor (condensing) coil. Be sure to turn off the power source before servicing this.