Tip & How-To about Heating & Cooling

Furnace issues? Read this first!

Many furnace troubles can be attributed to a dirty air filter. A dirty filter makes the convection air blower work harder than normal increasing the electrical consumption of the furnace, it will not allow enough air to the heat exchanger causing it to over heat and it will take much longer run times to heat your home. It is easy to check your filter and very inexpensive to change it. There are two typical areas where filters are located, one is in the return air duct or Plenum next to the furnace and may have a metal cover that slides off or held on by a screw. The other typical area is inside the furnace cabinet in the blower compartment. You can purchase basic filters that catch larger particles or spend a few more dollars on a pleated filter that will not only catch smaller particulate, it will last longer because of the more surface area.

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Bought a house with Lennox G12Q3-82-3 furnace. It doesn't look like electronic ignition. A sticker showing AirMedic Electrostatic Air Cleaner says it was installed 10/1992. Doesn't work.


Here's some borrowed info.:
`These are classic symptom of a limit switch opening. Can't guarantee that is what is going on, but here is some things that can cause the limit switch to open:

1) Low air flow. This can be caused by dirty filter, dirty blower wheel, dirty air conditioning evaporator coil, restricted or collapsed ductwork, blower motor running the wrong direction, blower running on too low of a speed, defective limit switch, or a combination of several of these factors. Inspection along with measuring the temperature rise will find most of them.

2) Heat exchanger failure. Split or burned through heat exchanger

3) Over-fired furnace. If you have eliminated everything in section 1 and 2, and the temperature rise through the furnace is still high, you need to check the furnace to make sure it is not burning more fuel than it is designed to burn. If it is a natural gas furnace, you can check the amount of fuel that is being burned by clocking your gas meter.

Here is a link that will tell you how to use your gas meter to calculate the BTU input of your furnace. It should never be more BTU than the furnace's rated input.
http://www.bacharach-training.com/referpage/clocking_gas_meter.htm

The problems you have could be potentially hazardous. If you are not able to aggressively find the problem on your own, you should hire a professional to look at the furnace immediately. The G12 furnace is getting relatively old. If you have never had it professionally inspected (sounds like you haven't), you probably should have a professional look at it immediately.' END QUOTE
This might cover your problem? don-ohio (:^)

Dec 19, 2016 | Heating & Cooling

1 Answer

why does furnace heat cut back?


You might try checking your return filter. The new filters (pleated 3 month, ie real expensive ones) cut back your air flow 35% from the amount the regular 30 throw away allow. When air flow reduces the temperatur from furnace increases and can cause inadvertant high temperature limits to trip. If you are using a clean return filter, next you need to physically observe the air inlet side of your cooling coil to see if it is blocking air flow due to being dirty. If you have trouble with seeing the inlet, you might need to get a professional to take the air handler apart.

Oct 29, 2012 | Goodman Manufacturing...

1 Answer

My Payne furnace is NOT producing the desired heat anymore. Any ideas?


Hello, it could be shutting down on it's high limit switch due to a dirty air filter, dirty blower wheel, weak blower motor. Usually this would cause the furnace to shut down before it reaches the desired temp.

Dec 30, 2011 | Heating & Cooling

1 Answer

I have a goodman gpmn furnace. The ignitor lights, and then the flames turn on, then the blower kicks on, and about 30 seconds later the flames turn off, and the blower continues to blow air. We have tried cleaning the flame sensor, and to no avail. Also the indicator light is blinking in sequnces of three.


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.

Feb 15, 2011 | Goodman GMS90703BXA Heater

1 Answer

miller furnace model M3RL080 BW, code flashes open limit switch or external load on W, I bought a new limit switch, the furnace runs for 5-10 minutes then the flame goes out, the blower keeps running and the same code flashes.


Check your furnace filter any Limit fault code usually relates to airflow...Not enough...causes the furnace to run too hot and shut off....the furnace can be too big for your house if its new...the ductwork can be too small , also make sure your return air vents are clean and unobstructed . Your furnace can be running too long a cycle ....also if you have central air conditioning the coil for the AC in the Furnace can be dirty...restricting airflow...if all this seems ok you can usually increase the fan speed or try tunning the fan in the "On" position on your thermostat this will promote better circulation

Oct 25, 2009 | Heating & Cooling

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