Tip & How-To about Heating & Cooling

Gas Furnace Troubleshooting With an Electric Meter

Normal 0 MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman";} The gas furnace is on the blink and you need to figure out what is the reason why the heater isn’t heating. Grab your electric meter, preferably a digital one, and we’ll check out some of the possibilities.

In your gas furnace find out where the power enters. Check the voltage between the black and the white wires. Make sure that the black wire is the hot and the white the neutral. Reversing these wires can make intermittent problems.

We have power to the unit, so let’s check further. If you turn the power on and the purge blower and the main blower both start to run then you probably have a high limit reset tripped. Look for the limit switch or switches to reset them. A little snap when you push the red button on the back will let you know that you found the right one. If there are no reset buttons then check for continuity across the terminals. If the switch is open then you need to replace it.

If your purge blower only runs but nothing else happens then you have one of two other problems. Either the igniter is bad or the pressure switch may be bad or the flue blocked.
Check the pressure switch first by seeing if you get voltage across the terminals of the switch. If the switch is closed like it should be with the vent fan running then you will not get a voltage across the terminals, this is good. Go on to check for the presence of power going to the igniter.

Many gas furnaces have an igniter that is very fragile and cracks easily. A small crack will keep the little bugger from getting hot and being able to light your furnace. Pull the plug apart going to the igniter and check for power. You may have to recycle the power if you have had it on for any amount of time. Often the furnace brain will time out the igniter try for ignition and will not have power to it continually. Also the power will only stay on for a few seconds when it does try, so you need to be ready and watch carefully.

If you are getting power to the igniter and it is not heating up then you have a bad one. This often will only be visible by a fine line of white dust on the surface of the igniter. This is the white line of death for the igniter and indicates a crack in it. Purchase an igniter that is compatible with your furnace or it may heat up too fast or not fast enough to work with your model furnace.

Hopefully this gives a few more tips to help you trouble shoot your gas furnace. As always, be very careful around and handling electrical parts. I have been zapped a few more times than I care to remember!

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I have a proselect thermostat psts11p52 that's 3 months old. So is the furnace. The AC works fine. Today i set the heater because it's cold and the temp stays at 68. These are my steps. - switch to HEAT - press HOLD - hold up arrow till it blinks then change to desired temp. - let go. i check to see and the desired temp is there. - it's been on for 30 min and the draft temp has stayed the same as well the temp on the thermostat. The HOLD shows and HEAT is blinking which I assume means it's heating up. Any ideas?

I'm thinking the heat blinking means its calling for heat and its not completed the Rh to W1 circuit yet. Once the circuit closes, the blinking heat will go steady....usually. Or if the thermostat is satisfied, it will stay steady and not blink...

I guess your thermostat could blink whether its mode is satisfied or not because I am not familiar with that particular stat. You forgot to say if the furnace is gas or electric heat, so if its gas, it sounds like it could have misfired and locked itself out. Go to the furnace, and cycle the power switch that should be mounted on the side. This will reset the controller and give it another attempt at firing correctly. If it continues to lock our after several attempts and you still have no heat, you have no choice but to call for service.

If its an electric furnace, there isn't much you can do but call a technician for a service call.

Dec 30, 2014 | Heating & Cooling

1 Answer

my goodman furnace 80703 fan comes on ignitor glows burner starts , cuts off in 10 secs,furnace starts cycle again. home no heat

I am not a furnace tech but, there are several inputs to a gas valve. There must be an 1) electrical/mechanical indication that there is a draft fan running (to move potentially explosive gas so it doesn't accumulate), 2) adequate gas pressure to the valve, 3) the thermostat must be calling for heat 4) and electrical indication that there is an ignition source. In your scenario, you have the source of ignition, the gas valve is picking up the burner but the gas valve believes there is something missing so it shuts off the gas to the burner. In this case, I suppose you might not have enough gas pressure (is another gas appliance running or is the line to the furnace too small?), a thermocouple probably isn't the problem since the burner wouldn't pick up if the gas valve didn't believe the ignition source wasn't good enough. You could have a plugged chimney or exhaust pipe if it is direct vented since there is also a pressure switch that detects whether there is enough draft once the burner picks up. Really should call a furnace person especially if you don't have a carbon monoxide detector that you trust. If you think you are capable of continuing, you could jumper the various inputs the the gas valve one by one until the burner picks up and stays picked up. Whichever terminals you jumper that accomplish this, is the culprit. Look at the schematic on the side cover to the furnace for this information. Hope this helps...

Oct 01, 2011 | Goodman GMS90703BXA Heater

1 Answer

my ruud furnace pressure switch is stuck open

If it is stuck open you will need to replace the switch....

Here is a tip that will help you try to figure out why your furnace is not working.

Basic Furnace or Heating System Troubleshooting


Dec 27, 2010 | Dayton Gas Furnace Heater

1 Answer

goodman furnace went out. Light blinks four times

Your main limit switch is activated. Maybe for good reason. This switch keeps the furnace from overheating. I have the same problem right now and I think my a/c coil may be blocked, limiting air flow through the heat exchanger and the furnace. Does your gas and main circulating fan come on for a few minutes before the switch activates and the light begins blinking?

Check your furnace filter and any return air ducts in your home - see if they are blocked or restricted.

Jan 14, 2009 | Goodman GMS90703BXA Heater

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