Garage Heater burner won't ignite

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Old 01-10-09, 02:32 PM
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Garage Heater burner won't ignite

The furnace is a Dayton 3E404 B gas heater. The pilot light is lit, the blower comes on, but the burner will not ignite. Not sure what the problem could be, need help trouble shooting, please.
 
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Old 01-10-09, 05:23 PM
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You have AC power because the fan turns on. The next step would be to verify that you have 24 VAC power at the point where the thermostat wires connect to the furnace.

Do you have an AV voltmeter and understand how to use it?

Measure the voltage from ground (the furnace chassis) to first one and then the other thermostat wire with the thermostat turned up, calling for heat. What do you get for a reads?
 
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Old 01-10-09, 05:32 PM
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is that a new install?does the stat have a FAN ON on it ......if not why is the fan running does the stat control the fan when you go back and forth with the temp dial?
 
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Old 01-11-09, 09:46 AM
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We checked. The reading is 29.
 
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Old 01-11-09, 10:37 AM
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Well, 29 VAC seems high, although that would be unusual.

I'm supposing you found that voltage on both sides of the thermostat wire, verifying that the thermostat is turning on the heater.

You need to continue to check for that voltage as it moves, wire by wire around the heater. With a presumably old unit heater, it probably goes to a limit switch and then to the gas valve.

Are you getting voltage to the gas valve? If so, the gas valve relay may be burned out.

You'd want to disconnect the wires to the gas valve and measure the resistance across that relay coil. If it's an open circuit, the gas valve needs to be replaced.
 
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Old 01-11-09, 01:37 PM
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Had it been working up til now this season? Or is this the first time you tried to use it this season? (Reason for question is sometimes gas valves stick closed at first of season and can be whacked with a screwdriver handle to free up during the call for heat. I had 2 this year that I "fixed" this way -no return calls to either, for last 2? months)

What is your gas supply? Any disruption in gas service or ran out of propane, prior to this?

Any way to know if gas valve attempts to open? If you hear a a small click sound at gas valve to know that it is at least trying. If click is heard at time stat is turned up or just thereafter in case relay is involed), you can try to set off flame with long-match type lighter. And/or if on natural gas, check 1/4 or 1/2 foot dial on your gas meter to see if it turns everytime the gas valve tries to open/to see if it opens.

Also, if click is heard or even felt with your fingertips placed on gas valve, at call for heat, and depending on what you learn about seeing if there is some type of gas flow or not, you could always close off the inline gas valve and then disconnect gas line just before the furnace's gas control valve at the pipe union or gas line trap, and confirm if good gas is present or just bad air. And by reconnecting and turning on inline valve again you may cause regulator/vent to jar free or gas valve to jar free. If there is some issue with the gas.

If no click heard or felt at gas valce, then forget some of what was said and confirm if electrical getting to gas valve with call for heat.

Do yo have a spill switch at the vent that maybe permanently high limited? If you do, and it was tripped, it will stop current from getting to gas valve. Some are resettable with small push button in between the 2 wires.
 
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Old 01-11-09, 04:38 PM
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It was working up until this time. We turn it down low at night and this time it did not kick on. There is a click when you adjust the thermostat. We tried to tap it with a screwdriver, but this did not work. This is a natural gas heater. There has not been any interuption of the gas supply. It does not appear to be an electrical problem. The pilot light is on, when the thermostat is turned up the unit clicks, but you can not hear the gas going through the line. The fan eventually turns on but it is useless as the burner was not able to ignite. It must be a problem with the gas valve. Is there something that regulates the valve or could it just be faulty, if this is the cause of the burner not igniting.
 
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