Goodman heater "twinning" problem

Hello, looks like you limit switch keeps opening because your furnace is overheating, Check your air filter and blower wheel to make sure it is not dirty and make sure you blower motor is moving at the proper speeed. Usually when air flow is cutoff the limit switch will open.

On - OK
1 Blink - Ignition failure. Check Gas flow, gas pressure, gas valve, flame sensor.
2 Blinks - Closed pressure switch. Check pressure switch (stuck in closed position).
3 Blinks - Pressure switch - failre to close. Check venter, pressure switch, vent blockage.
4 Blinks - Open limit switch. Main limit or aux limit are open. (My comment - Means overheating in chamber. Often result of blocked intake air. Bad filter. In my case, plastic wrap had been sucked into the intake. )
6 Blinks - False flame sensed. Check sticking gas valve.
Rapid continuous blinking - Incorrect twinning, incorrect primary polarity. Reverse transformer secondary leads, reverse primary wires.

Closed pressure switch can be from dirty combustion vents, bad chamber pressure - like missing screws, maladjusted gas pressure, failing pressure switch, loose hoses, moisture in the hoses or fan blades The switch need to be closed to ge the unit to work

You might need a new flame sensor, but most of the time they can be cleaned an will work well after cleaning.

The flame sensor or "flame rectifier" has gone bad or the wiring is cut. Replace flame sensor.

This furnace should have a trobleshooting diagnostic led flashing light. Each blink (for example 3 blinks means open limit switch) has a particlur meaning. On the bottom panel has an explaination on what the blinks mean. But in the meantime check 24v at the gas right as the ignitors light. If you have 24v and the gas valve doesnt let the gas thru then the gas valve might be defective. I usually put 24v dircetly to the gas valve for 2-3 seconds to see if gas will come out. It is loud enogh to hear as well as smell. If you dont have 24v as the ignitor tries to light then check the air pressure switch. Also follow the wire off the gas valve. One is to ground. Make sure the gas valve is grounded. Follow not the grounded wire but the other one. Find out where the 24v power stops.

If the igniter lights the burners the ignitor..... is not bad. Its like a light bulb.... it works or ot doesn't.
You are describing a dirty flame sensor. Dishonest contractors will sell you a new ignitor but clean the flame sensor when the are installing the ignitor. It is located at the opposite end of the burners than the ignitor. It has one wire going to it. Remove it and clean the rod with a piece of fine grit sandpaper. this should be done every year before heating season.
Good luck

limit switch is on the heat exchanger black plastic about 1and1/2 in. by 2 in. with 2 wires going to it , it has 2 screws holding it in take it out and check it with an ohm meter and you should not have a reading if it is good

There is a flame sensor located in the same area as the ignitor (usually on the other end of the burners). remove the flame sensor with the power off. Then use steel wool or light sand paper to clean the silverish end. Reinstall the sensor and ToDA you are done! Best of Luck!

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).

Furnace attempted to start but failed after so manay tries. This may help you.

Sequence of operation, Gas Furnace.

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).

This is why we technicians earn the big bucks!