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I have a problem with my heating system. It is about 10 years old and has had the ignitor, combustion blower motor, and programable thermostat replace in it's lifetime. The system worked great last year. This year has not been so good. The system was checked and cleaned last month. What is happening is the blower kicks in and the burner cut off after a few (15-20) seconds. I tried shuting down system and turning off power to reset. When you turn heater on this is what happens 1. Combustion fan comes on for 35 seconds 2. Ignitor fires about 14 seconds 3. Gas vavle opens and ignites. Burner runs about 45 to 65 seconds and goes out. 4. Relites in about 45 seconds, this cycle repeats several times. 5. Main circulating blow comes on and about 20-30 sec burner goes out.Then the blower cuts off, a little later 30-45 seconds the burner relites and we start all over again. The temp inside of house will not go above 63 no matter what you set thermostat at. System can run all night but never cuts off. The unit uses LP Gas, No codes on control panel. System Model# MMBB090ABHR06. Temp at vent 79-83 when blower runs.

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Sounds like its not proofing flame. it has a sensor usually like a needle sticks out into the flame that tells the gas valve the flame lit and is burning so its ok to keep sending gas, if its fails to proof flame then burner shuts down, then it tries to relight 3 times then locks out on fail safe. the blower will sometimes run continually once that occurs to highlight a failed condition. every time you reset it will try again 3 times then shut down. lp gas is very dangerous, even i do not work on it as the gas acts like gasoline and lays around. not like natural gas that disperses well. if you see the flame sensor try gently cleaning it with a little emory cloth. also a loose ground can cause this. check tio be sure any green wires are snug , they actually flow volts to ground through the flame on some to proof, thats why no ground no flame. if that fails then the board is most likely problem. change wire for wire , or get generic replacemant and follow directions exactly. good luck.some ignitors act as a flamre proofer as soon as they are done igniting! rarely do they fail to perform both funtions.

Posted on Nov 21, 2008

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Pro 4000 thermostat is set on heat 73 but inside temp is 64 how do I fix? It's only about 2 weeks old.


If you switch to cooling mode and run that test, it may help pin down the problem with thermostat. However, the cooling wiring is independent of the heating system for most of the wires. Checking if the fan runs in the fan-only setting will check if that message gets to the HVAC system from the thermostat. (This only applies for forced air systems.)

There are two possible sources of the problem. The problem could be at the thermostat. Sometimes one (or more) of the conductor wires came loose from their terminals. Alternatively, one of those wires has broken. Pull the thermostat off the wall plate by pulling up at the bottom. Make sure that all of the wires are secured fully (either by the screw or push-connection). If any wire is damaged, cut off the broken section and strip a bit of insulation. Then secure the wire. (Use the labels to make sure that they are at the correct terminal.)

The alternative is a problem at the furnace. Check for power first. A tripped circuit breaker is not unknown. After that, the could be a problem with the control system, the ignitor (for gas or oil heat sources), a blockage at the exhaust or air intake (for high efficiency heating systems) or the blower motor (for forced air systems). Some heating systems have LEDs that indicate an error condition. Look to see if there is any blinking lights. Use your furnace manual to check what those codes may mean.

Clear around the exhaust outlet and air intake if you have any debris or snow/ice near there. Make sure to take safety precautions for a roof/chimney exhaust. Look at your furnace manual to see if there is a test option.

For my current HVAC system, you can test with a jumper wire. A few months ago, the heat didn't come on and that test proved that the blower motor didn't spin up. (The system has an interlock that stopped trying to provide heat when the motor doesn't spin properly.) A new motor was installed and the problem was solved.

I hope this helps. Please add a comment with more information about the heating system that you have and any error codes if you need extra assistance.

Cindy Wells
(I have a gas-fired electric ignition furnace. Without the blower, the furnace would overheat so it locks the gas valve and ignitor.)

Feb 12, 2017 | Heating & Cooling

1 Answer

I have a 10 year old honeywell furnace controlled by a SV9541 smart valve. We finally had to switch to heat but no heat. Tried restarting - system does nothing. Checked to make sure the gas line is open...


Sounds like the Ignitor unplug the ignitor check for continuity if no continuity replace Ignitor or you can usually see the crackon the Ignitor with white residue.

Sep 18, 2013 | Honeywell Programmable Thermostat Heater

1 Answer

No gas is entering the unit and it does not ignite. we live in Arlington Texas, who can help repair the heater.


a servicer for 18 years in the dfw metroplex... the sequence of operation is as follows ...
the thermostat calls for heat
the enducer draft motor comes on and then pulls the air out of unit and closes the pressure switch located inside the burner side of the furnace also..it has a small hose going from it to the enducer draft notor housing... after the pressure switch closes then the ignitor should come on or if a spark module it will spark...after if either gets hot enough or sparks the gas valve opens and unit should lite. after reaches temp the blower will then come on... this is for a 10 year old unit and newer
if you have a older system with a pilot system you should have a pilot light on already and upon the call for heat the gas valve should open and light then when temp rises the blower motor will come on... reset unit either by unplugging or turning off power and then turn on again and watch where does it fail and does it have a circuit board if so it will most likely have a fail code on it....

Jan 11, 2011 | Heating & Cooling

1 Answer

Furnace will not light burners and blower motor doesn't come on, but exhaust fan comes on immediately when turning furnace on. Turned on A/C to make sure blower operates and it does. The combustion...


The reset button should be a small round red button that you just push in to reset. If the induced draft motor comes on as soon as thermostat calls for heat then the next thing to check is the ignitor. It may be a hot surface or spark ignitor.It should glow or spark depending on the type,and you should be able to see it clearly. The ignitor should be located by pilot assembly right beside burners. If the ignitor does not work the furnace willnot procede in lighting sequence. If ignitor is not working then it must be replaced. Usually this is pretty easy if you can get repair parts.Remove screw holding ignitor in place and disconnect wires. Install new one and try it. Good luck. Thanks

Nov 19, 2010 | Heating & Cooling

1 Answer

Outside heating unit runs all the time


Usually when the furnace blower motor runs all the time
The limit switch or rollout switch is usually open or bad.
The furnace board is seeing that one of those switches is open, so it brings the blower on to try to get the heat out of the combustion chamber area, so the switch will close. But if the switch is bad and won’t close, the furnace board will keep the blower running continuously.

Feb 19, 2010 | Heating & Cooling

1 Answer

When turning on my Quadra Fire 1000, turn up the thermostat the orange light should come on signaling that it is calling for heat, but the only thing that runs is the combustion blower. What to check?


Hi, I am not sure of the sequence of operation of this heater, but on most other heaters with a combustion motor on them, it will come on 1st. and then it will establish that the pilot is coming on , glow plug, or hot surface ignitor. I would check this to see if what ever ignites it is coming on next. This would be the sequence of a heater. Good luck,
Shastalaker7

Nov 24, 2009 | Heating & Cooling

1 Answer

It's not lighting it's not working I see motor is running and I think gas coming out but it's not lighting I turn off the funance


Turn the power off to the furnace, turn the thermostat to the highest heat setting then turn the power on. The fan may start for a brief period, then the combustion blower will start, after approx 90 seconds, the ignitor will light and heat up. You should be able to see a glowing in the burner lens. If you do not see a red glowing, similiar to a car lighter, that would indicate the ignitor may have failed. If after 3 attempts, the systems fails to light, there is a light on the circuit board that will flash, the number of flashes will indicate the reason for the fault.

Nov 13, 2009 | Goodman GMS90703BXA Heater

1 Answer

I have a Goodman air heat unit that will not come on.


On a call for heat, the 24 volt thermostat sends a signal to the control module. The control module will indicate a call for heat with a light on the control either blinking or remain solid depending upon model. The inducer (exhaust) blower will purge all gasses from the furnace and pressurize a pressure switch. Once the pressure switch tells the module to continue, the electronic ignition will energize and send 120 volts to the ignitor. The ignitor will glow and you will be able to see it if viewed thru the small inspection port. Once the ignitor gets hot enough, it sends a signal to the module opening up the gas valve (24 volts). Either a pilot will come on or the burner tube will ignite then spread the flame to all burners. Lastly a safety sensor will be looking for a certain temperature within a few seconds and the furnace will continue to operate and the room air blower will turn on in a minute or two.

What could go wrong? The unit will not run if there is no signal from the thermostat (bad thermostat or broken wire), the control module does not sense a signal from the thermostat (bad control), the inducer does not energize (bad motor), the pressure switch does not close (blocked vent piping, bad switch, plugged condensate hose), the ignitor does not energize (bad control, bad ignitor), the gas valve does not open or there is no gas (bad gas valve, broken wire, no gas), the pilot does not lite (dirty pilot), the burner does not lite (bad burner, plugged orifice, not enough combustion air), the flame does not spread to each burner (bad flame spreader, dirty flame spreader, more bad burners), the flame safety sensor does not detect flame (dirty or bad flame spreader, bad flame sensor, broken wire, bad control), or the room air blower does not energize (bad fan motor, bad control).

Most newer furnaces will have a diagnostic center or control built into the control module. You may be able to view it as it is running thru a small viewing port. Some models will require the removal of an access panel prior to finding it. On the reverse of the access panel, there will be a diagnostic chart that will aide you in understanding any error code recorded (usually a blinking light).

Jan 27, 2009 | Goodman GMS90703BXA Heater

1 Answer

I have goodman gmp heater dose work for few mintes


Sequence of operation on your gas furnace may help diagnose your problem.

On a call for heat, the 24 volt thermostat sends a signal to the control module. The control module will indicate a call for heat with a light on the control either blinking or remain solid depending upon model. The inducer (exhaust) blower will purge all gasses from the furnace and pressurize a pressure switch. Once the pressure switch tells the module to continue, the electronic ignition will energize and send 120 volts to the ignitor. The ignitor will glow and you will be able to see it if viewed thru the small inspection port. Once the ignitor gets hot enough, it sends a signal to the module opening up the gas valve (24 volts). Either a pilot will come on or the burner tube will ignite then spread the flame to all burners. Lastly a safety sensor will be looking for a certain temperature within a few seconds and the furnace will continue to operate and the room air blower will turn on in a minute or two.

What could go wrong? The unit will not run if there is no signal from the thermostat (bad thermostat or broken wire), the control module does not sense a signal from the thermostat (bad control), the inducer does not energize (bad motor), the pressure switch does not close (blocked vent piping, bad switch, plugged condensate hose), the ignitor does not energize (bad control, bad ignitor), the gas valve does not open or there is no gas (bad gas valve, broken wire, no gas), the pilot does not lite (dirty pilot), the burner does not lite (bad burner, plugged orifice, not enough combustion air), the flame does not spread to each burner (bad flame spreader, dirty flame spreader, more bad burners), the flame safety sensor does not detect flame (dirty or bad flame spreader, bad flame sensor, broken wire, bad control), or the room air blower does not energize (bad fan motor, bad control).

Most newer furnaces like yours will have a diagnostic center or control built into the control module. You may be able to view it as it is running thru a small viewing port. Some models will require the removal of an access panel prior to finding it. On the reverse of the access panel, there will be a diagnostic chart that will aide you in understanding any error code recorded (usually a blinking light).

Dec 10, 2008 | Goodman GMS90703BXA Heater

2 Answers

Thermostat wont turn on heater Robert Shaw 9600 prog.


I have a thermostat 9600 Robertshaw and I have to use the trip switch to start my furnace. Then it reaches the temperature and sometimes it will kick in by itself but majority of the time I have to trip it. I have changed the batteries cleaned the thermostat,and reset it. Is it time for a new thermostat and can I replace it myself. Thanks

Nov 06, 2008 | Heating & Cooling

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