I have a Fraser-Johnston closet mounted Natural gas using Central heating unit. The unit has been off all summer and I just changed the filters and relit pilot. When I set the thermostat I hear it click at the right temputure for it to turnon but the burners dont even try to light.. Could it be just a thermostat issue or do i need to start shopping for a new unit.. I did not see a flame sensor.

Is the unit equipped with some type of Summer/Winter switch? If you just changed the filters, are the front panels securely attached to assure the interlock switch (if present) is engaged? Is the selector knob/lever on the gas control in the correct position?

No. It is pretty basic heating only unit. the front panel is on but there is no sensor that would inhibit from starting. the knob is turned to on

I would start by attempting to verify the power supply to the unit. Check any switches, fuses, and/or circuit breakers present. If the thermostat has a fan selector switch, move it to "ON" and see if the blower runs.

KC13 thank you for your quick responses. I checked circuit breakers and switches for the unit... all are on there is no seperat setting for fan or blowers.

Just for the heck of it (if you haven't already), try toggling the main power supply switch off/on a few times. If it is old and the contacts are burned/oxidized, this may restore function until you can replace it.

Thanx. I will give it a shot. nope...

If this is a heating-only system with no fan selector at the thermostat, there are probably only 2 control wires in the thermostat circuit. Try connecting them directly together (bypass the thermostat). Turn power off, connect wires together, and restore power. If this works, the thermostat is the culprit. This can be done either at the thermostat location, or where the control wire connects to the furnace.