Hello,

The Red LED on the circuit board on my Goodman Air Conditioner is OFF. The code on the furnace cover panel says that this means "Control Failure". The circuit board model number is B18099-26. Any help on how I can go about debugging this problem is much appreciated.

Thanks.

First thing to check is for power to the unit (more accurately, power to the control board). No power=no led. Next, check to make sure the three amp fuse on the board is not blown. If good, check to make sure you are getting 24v on the secondary side of the transformer. If all power checks out correctly, and the led is still not on, then a new board it is.

Thank you very much for your help. My mistake; the LED is actually fine. When I opened the furnace panel door, the switch that is depressed by the panel door got released and hence the LED was OFF. Once I pressed the switch, the LED came on and remains steady lit. The fuse (marked "E"; I assume this is the 3 amp fuse) is also intact. I measured the voltage on the secondary side of the transformer and I get 24 volts (actually 27.3 volts). Thank you in advance for any help you can offer as to how I should go about tracing the fault from here. Once again, I really appreciate your responding to my query.

Okay, so we know we have the correct power to the board. Next, can you tell me exactly what the problem is, or what is not working. Do you have no heat, a/c, fan, etc. The more info you can give me the better I can help.

Thanks. I have no a/c. When I lower the temperature below the displayed room temperature on my thermostat, the thermostat clicks and I see the cooling sign (like a snow flake) come on the thermostat display. However, the furnace fan does not come on. I changed the fan switch on the thermostat from "auto" to "on" but this did not make a difference. The outside condenser fan also does not come on but I'm assuming that will come later. I guess the furnace fan needs to come on first. Where can I go from here ?

Is the snowflake flashing, or is it on steady? If it is flashing, it means the time delay for a/c is on. Usually will flash for about five minutes then come on steady, at which point the blower and outside unit should come on. If the snowflake is on steady, and the blower and outside unit still aren't coming on, then there are a lot of options for this problem. Pop the face of the thermostat off and jump r to y while having someone watch to see if the outside unit starts up. If it does, you have a fualty thermostat. Let me know what happens.

Thanks again for your help again. The snowflake does come on steady and I confirmed that the thermostat is not faulty. I have two hvac units, upstairs and downstairs and I swapped the thermostats but continue to have the same problem.

I would jump r to y on the control board and see if the outside unit comes on. If it does come on when r to y is jumped (dont forget the door switch) then you have a bad thermostat wire between the stat and furnace. Just got to take this one step at a time to eliminate low cost items vs high cost items, like control board.

When I was trying to measure voltages on the circuit board yesterday, the A/C suddenly came on and worked last night. It was working until earlier this evening. I had to go out for the back to school night meeting and was going to reply after I came back but now it stopped working again. I see a difference though when I lower the temperature now. I see that the snowflake starts blinking and then becomes steady like you said. However, the a/c does not come on. The snowflake just continues to stay on steady. Any idea what might be happening ?

It is a little late in the night now to go up in the attic but I will go up first thing in the evening tomorrow around 6:00 pm ET after I come back from work and jump the r & y on the control board as suggested by you. I'll let you know what I find after doing this. Meanwhile, if you think of something else given the fact that the unit started working and stopped again, please do let me know. By the way, you mentioned that when I jump the r & y on the control board, the outside unit should come on. What about the indoor unit fan ? Shouldn't that come on first also ?

Once again, thank you very much for all your help. I really appreciate the step by step guidance.

Could be a loose wire, since it started working when you were messing with the control board. Jumping r to y on the control board should definitely kick the outside unit on, and may or may not kick the indoor blower on depending on the circuitry of the control board. If it is a newer goodman, r to y should kick both the outdoor unit and the indoor blower on, but there will be a few second delay before the indoor blower kicks on.

Sorry for not reporting back on this earlier but we were out of town for the Labor day weekend and spent the last four weekends dealing with a flooded basement due to the recent heavy rains here in MD.

Anyway, I shorted the 'R' & 'Y' points on the circuit board as suggested but nothing happened. The AC did work on and off during the past 3-4 weeks but seems to have stopped altogether again. It has been very chilly here in MD for the last 2-3 days and I switched the system to heating and it is not working in heating mode either.

What can I try next ?

Thanks in advance.

Is the led light still coming on steady? This may get a little tricky to trouble shoot over the internet. It may be time to get a pro in there. They should be able to trouble shoot this in short order and have you up and running again in both heat and a/c. Goodmans are really pretty easy to troubleshoot and repair when a pro can get their hands on it. Just to many variables here without putting my multimeter to the unit. Good luck, and please let me know what you find.

You know what ? The LED was NOT ON!! I did notice that yesterday but it did not ring a bell :( I checked the fuse though and it was okay. Does that mean that I don't have 24V ?

That was yesterday. Today, I wanted to chase down any loose connections that I may have. I started with the thermostat, checked all the wires and tightened all the screws. The screw to the "R" wire was loose. I was able to tighten it a couple turns. After this, both the heating and cooling are now working. Does this make sense ? Of course, I did not check if it was working just before I tightened the screws. If it was only a loose wire from the thermostat, shouldn't it have started when I jumped the "R" & "Y" wires as suggested by you ? Can the LED be OFF due to the "R" wire from the thermostat being loose ?

Also, when switch back from heating to cooling, the snowflake was blinking and NOT steady and the AC did not kick in immediately. From what you've told me before, I assume it would have kicked in after some delay. Most of the time, I've noticed that my snowflake comes on steady. Why does it come on blinking some times ? Is there a sequence of operation or some logic to this ?

Sorry for so many questions but I would like to understand this better as I'm not sure my problem has gone away. Like I said, the system has worked on and off in the last few weeks since I'm having this problem.

Thank you very much for all the help, pointers and guidance so far. I would appreciate as much detailed info to my questions above as possible.

The loose connection on the stat would not cause the led not to glow. So, Im stumped on that one, unless the door switch wasn't fully depressed. When the snowflake is flashing, it just means the time delay for the a/c is on. Once the call for a/c is satified, the stat won't let the a/c start up again for usually around five minutes (hence the flashing snowflake). After the five or so minute delay, the snowflake should come on steady and the a/c should kick in. There usually is no delay for heat. The delay on a/c is to protect the compressor from hard starting. It allows the pressures in the a/c system to equalize before letting the compressor to start. Hope this all makes sense. Glad to hear your system is working now. However, if it fails again, like I said, it would be tough to trouble shoot without seeing the actuall failure in person. Just to many options. Hope it was just a glitch, and your working with it somehow cured the problem. Fingers crossed.

Thank you for everything once again. I will call a tech if the system acts up again.

Hello, just wanted to close the loop here. Since the LED was not glowing when I opened the unit the last time, I opened it up one more time to check the voltages and sure enough, there was no 24v. There was no 110v on the primary side either and I traced the problem back to the ON/OFF switch in the attic. You know the hole in which you push the 14 gauge wire; a chunk of the plastic housing on the outside of the switch had chipped off and the metal clip which should have held the live wire tight was loose. I wish I could upload the picture so you could see immediately what I mean. Anyway, I guess the loose connection was acting up and hence the intermittent working all along. Wonder how a tech would go about this in the limited time he has to debug if the contact is good at the time of debugging the problem. After replacing the switch it has now been working consistently for 4 days, just in time for the cold weather that set in here in Germantown, MD starting this past weekend.

Once again thank you very much for all your help and patience in trying to help without actually being able to, like you said, get your multimeter on the unit!

I have a goodman furnace. When the heater kicks on the fan does not come on and the burners will burn for a while then its shuts off. The led blinks for times four times after it shuts down. I have manually spun the blower and then hit the switch and it would work. Could it be something with the power going to the blower?

Hi Newby. The four blinks is indicating that the high limit is open due to overheating. This is of course due to the blower not kicking on. If the blower runs fine when you give it a manual push by hand, I would start by replacing the blower motor capacitor. It may be as simple as that, and they are cheap and easy to replace. If that doesn't cure the problem, you will most likely need a new blower motor. When replacing the capacitor, make sure to get an exact replacement as far as MFD, or UF rating goes.