Home Improvement → Re: Gas Furnace not always turning on

This!

I have two Goodman furnace/air handlers in my attic, circa early to mid 90s. Neither of them have (well, had) view ports to see the LED. In addition to the outer cover, they also have an inner cover so you can't see the control board even after removing the outer cover! Incredibly stupid design... And yes, opening the side panel turns off the power to the board, which does reset it. With my trusty drill and some clear packing tape to cover the holes, I can now see the LED's without removing the covers.

Yahtzee- this has been my problem. I can't see the blinking light due to no window and then a metal box covering the led light. I called the company and they said that taking off the bottom panel will not reset the buttons even though it turns the furnace off. Who knows if that is correct or not. The furnace has been working perfectly the last 24 hours. That is why this is such a problem. Some guy is going to come here and say everything looks fine to me.

This is getting more confusing by the minute. The blink code legend for your furnace is not the same blink code legend in the manual "iknow" posted. So, if you're seeing a "pulse", that is normal.

I'd suggest doing what jack b suggested. To take it even further, you can also take off the blower panel and hold in the door switch while keeping an eye on the LED. Of course, for this to do any good, the furnace will have to malfunction during that time. If it operates normally, you're wasting your time.

The trick is the furnace needs to malfunction and you need to be able to see the blink codes. The suggestion to drill a hole in the blower compartment door and leave the control board cover off is a good one, as that's really the only way you're going to be able to see what the LED is telling you when the furnace malfunctions.

Looking at the pic of the chart that you posted, and comparing it to the one on page 51 of the manual (which lists GMP as one of the models covered by that pic), they appear to be the same to me. Page 50 is correct in it's statement:

" A flashing red diagnostic indicator light on the control flashes a code for any discovered failures.

When the control is powered up normally, the light will be solid red for normal operation."

You're seeing 1 pulse, a long pause and then 1 pulse, the code for ignition failure. You need to be AT the furnace when the t-stat calls for heat. The light on the control board should be on, solid, with NO flashing, before the t-stat calls for heat. When the call for heat arrives you should hear the exhaust blower start running. It should run for about 30 seconds, then you'll hear a loud click as the gas valve gets energized. The ignitor should start glowing a fairly bright orange a couple of seconds after the gas valve opens, then the gas will ignite and start blowing blue flames into the heat exchanger.

If the flame doesn't light at all, then did you see the ignitor glow at all? Sometimes they crack and become intermittent. Replacing it is easy. Usually one screw holds it in place and the wires unplug from the harness.

If the ignitor glows but the flame doesn't light, then you have a gas delivery problem. If you aren't familiar with working with that stuff, then call a pro. You CAN blow your house up if you do it wrong.

If the flame lights, but goes out several seconds later, then it's most likely the flame sensor not sending the signal that the flame is present. This will turn off the gas and start the single pulse error flashing. It should also leave the exhaust blower running to remove any unburned gas.

When you power down the board and then power it up, the LED should come on solid.

The chart of page 50 shows:

Status Light On - Normal Operation

The chart the OP posted shows:

Status Light Pulse Rate - Normal Operation

I don't think "On" and "Pulse Rate" are the same thing.

I am with Sand on this one. When my furnace is working like it should be, I see a "pulse" happening with my LED light. There has to be something going on between the thermostat and the furnace. Somehow the furnace is not getting the message to turn on.

It would be interesting to know if the LED flashes when the board is first powered up. I believe it is supposed to be on solid. Both the units in my house are GMP models as well and the LED's on both are on solid unless there's a problem.

Post collision! I was looking stuff up.

I agree Harry but I don't think that it should be a solid light. I will give a call on Monday to the people who put this furnace in. The problem is that it was put in by a previous owner of our house. THat is why I am scrambling so much as they did not leave the manual with the furnace. And again, I am a complete novice at this. I have no clue what the hello I am doing. I understand things and have upgraded my house because I watch video and post questions on threads asking for advice from such places as this.