Why i turn on the thermostat, the fire won't light up. why is that?

Make sure the gas valve is turned to the ON position after you had it in PILOT position. Also check the thermostat low voltage wiring @ furnace...jumper the Red & White wires to bypass the thermostat temporarily. Make sure there is 24 volts on you low voltage circuit.

Glenn,
Many things could be wrong. First off, the exhaust fan turns always goes on when you turn on(up) the thermostat. It does that to suck out any residual gas in the combustion chamber. After about 10 seconds you should hear a click which is the gas valve opening to let the gas into the chamber. You should also hear a series of clicks for about 10 sec, which is the electronic ignition firing. If you hear the clicking of the ignition, but do not smell gas from the exhaust, then the gas feed is being blocked. If you don\'t hear the ignition clicking then the computer board is detecting a fault condition by one of its sensors: over-temp, water flow, exhaust fan . These are all in series and if one doesn\'t pass then the ignition won\'t fire.

Likely one of two things. The thermostat is stuck on or your gas valve is bad. Identify one of the wires going to the thermostat and disconnect it, if the burners shut off with the thermostat disconnected the problem is the thermostat, otherwise it will be the gas valve. All this assumes the unit is wired correctly and has not been changed. If your burners are not shutting off due to a bad gas valve or thermostat you are at risk to have a fire! Be sure to get this fixed immediately and it is unsafe to operate the fryer until repaired.

Maybe needs a new radiator, thermostat, how is the water pump?I had this engine for 400.000km.

Hi, if you have high voltage going to the unit and it will not fire up, then you are not getting control voltage to it. It takes 2 power sources to run it, high voltage for all of the motors and compressor, but 24 volts from your thermostat to fire it up.I dont know if you have a gas furnace, heat-pump or what. If its a gas split, you will have only 2 small thermostat wires coming into the contactor coil to fire it and close it to send power to all else.You may have a bad stat, broken stat wire, or a faulty transformer, but you have lost your 24 volts somewhere in the unit, and the 1st place to check would be the stat. Please keep me posted.
Shastalaker7 A/C, & Heating Contractor

If the engine won't fire up, but your starter turns over, you may want to check your timing unless you have a check engine light on. If the CEL light is on, have the codes scanned.

If the engine won't turn over with the starter or it clicks, have your battery tested at autozone or advanced auto parts. Replace the battery if it is bad. Else, have your starter tested.

If the engine still won't turn over and the battery and starter are tested fine, you may have a blown fuse, bad ignition switch, or a failed relay.

If the engine fires up but randomly dies and starts back up, you either have a failed sensor, failing fuel pump, clogged fuel filter, bad plugs or wires, or a failing ECU.

I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

All wireless wall thermostats are Millivolt controlled. rather than having an 18 or 24 volt (transformer) wired wall thermostat. Before purchasing any wireless wall thermostat, you need to determine what your oil fired boiler requires for activation. My experience tells me, that it's going to require either 18 or 24 volts. In which case a wireless thermostat won't work.

Hope this helped you and thanks for choosing FixYa.

Turn cylinder stat down , turn heating thermostat up . check setting on boiler thermostat should he on high see if it fires

Make sure thermostat is turned to 120 to 150 degrees Fahrenheit. Turn the thermostat down and back up to see if it ignites. If it lights put the cover back on and set it to temp you want it to be. if not, you have a bad thermostat.
Hope this helps.

this could be the thermostat has gone but most likeley its the copasitator that makes the machine start and stop and change directions if the machine runs and cannot change directions this will cause the thermostat to glow red WARNING THIS MAY CAUSE A FIRE