Lennox 80MGF Flame Roll-Out code when hot…

21:48: ______________________________________________________________________ Background: I have a Lennox 80MGF2 gas furnace. It’s about 9-10 years old. It’s connected to a Lennox HS25 condensor and a Honeywell digital thermostat. About 3 years ago, the circuit board went kaplooey. My “trusted” HVAC guy diagnosed this, but didn’t give me much for repair options. I searched the internet, found the replacement circuit board (kit 65K07 w/conversion to Heatcraft control, EGC-1), bought it and installed the new circuit board myself. It worked fine for the last 3 years. The Problem: Last Wednesday night I came home to a rather warm house. I noticed the thermostat displayed “-AC” (no 24V AC available to it). I’d seen this a few times before and went through the usual troubleshooting — taking the thermostat off and cleaning the contacts, swapping it out with the other thermostat unit in the house to isolate the problem, resetting the power to the furnace/blower, and that simply confirmed that something other than the thermostat was the problem. I noticed that the LEDs on the EGC-1 circuit board indicated a “Flame Roll-Out”, meaning the flame roll-out switch had opened, for which the stated remedy was to check the continuity of switch and for blockage in heat exchanger and then manually reset switch. Having no knowledge of what this meant, I think I determined through the instruction manual what the flame roll-out switches were and pressed the small buttons down on them. That did nothing, so I paged my HVAC guy. He was going to come out the next day on Thursday. A few hours into the night, the unit started functioning normally again, and we slept cool. Thursday afternoon comes around and the unit ceases functioning again, “-AC” is displayed. My HVAC guy shows up. My wife’s home and I’m at work. He is informed of the codes I found, but believes the circuit board is the culprit again (since it wasn’t outputting 24V AC), and that he shouldn’t really do a full service until that’s replaced. He knows I did it before so he suggests I do it again. I’m a little miffed at having to do it again, but figure it’s not unreasonable for a board to have a problem after 3 years in a hot attic, so I order the unit. It won’t ship until Friday, meaning I don’t expect delivery until Monday. Meanwhile, Thursday through Monday, the system keeps going down in the afternoon sometime and coming back up during the night, working until sometime the next afternoon. I can only surmise that it is definitely heat-related, esp. given the shorter duration of the problem on the afternoon where we had some clouds and rain for a while. Monday rolls around and after work I replace the board. Fortunately, since this was a direct replacement of the same exact board, all I had to do was remove and replace with all wiring staying the same. That I did. As soon as I restored power to the furnace/blower though and tried to turn things on, the same trouble code sequence for Flame Roll-Out began sequencing, and the unit would not function. “-AC” remained, yet the transformer to the circuit board was putting out about 27V AC. This time it stayed inoperative until 5 a.m., which is over 4 hours later into the night than it had previously resumed operation. Today (Tuesday) I was very busy at work, but my wife spoke to our HVAC guy. He didn’t seem to offer much in the way of advice on what to do or even offer any further help, since “he was taught that if you had power into the board an no power out it was the board that was bad” (wife’s paraphrasing of his comments). He also stated that if he’d known the unit came on and off during the night and afternoon like this, he wouldn’t have said to replace the board. He didn’t say what else he’d do though. Before I talk to him again, I’d figure I’d consult someone who may be a little more competent. I have a theory that the board is designed to interrupt power to the thermostat when it encounters a trouble code like it has encountered, and his lack of knowledge about its designed operation is part of the problem. My questions: Anyone experience this before? What is the complete course of troubleshooting action that should now follow? Your help is appreciated. A few parting thoughts follow. The Good: I have another A/C unit in the house to keep things from getting hot. The Bad: The nearly $300 I may have just wasted on a new circuit board — if that’s not my problem, anyone want a complete 65K07 ignition control replacement kit that’s only been used a couple days? The Ugly: The length of this, my first post here. [this message was edited by LCP on Tue 21 Jun 21:58] Replies: vgrobertson “Re(1):Lennox 80MGF Flame Roll-Out code when h” , posted Sun 15 Oct 21:34 ______________________________________________________________________ Good to see you figured out what your problem really was with your unit. Unfortunately, you learned a costly lesson in not always depending on your HVAC personnel to do right by you. Unfortunately, they are in business to make money and usually will not even try to diagnose your problem, much easier to just start replacing parts, at your expense. Whenever anything goes wrong with our appliances or just about anything in our home, we always turn to the internet for help, you generally can find a website which helps with troubleshooting and parts, usually FREE and can save you a bundle for some of your time in researching. As for your control panel, do you still have it? We would be interested in it if so. Please let us know. God Bless. Robertson foolio “Re(1):Lennox 80MGF Flame Roll-Out code when h” , posted Tue 5 Sep 17:58 ______________________________________________________________________ Hi, I was reading on your post about the lennox 80mgf. I encountered the same problem that you had. The AC guy quoted me $1000 for parts and labor. My question is, where did you order the EGC board? $300 is way cheaper then $1000. Any tip you can give me I really appreciate it. Thank you LCP “Re(2):Lennox 80MGF Flame Roll-Out code when h” , posted Wed 6 Sep 00:38 ______________________________________________________________________ I got my parts, both the new circuit board and the new flame roll-out sensor from cozyparts.com. I suggest calling. Since the problem in the above post was just a bad flame roll out senser (something like $20 if I remember correctly), I still have an extra replacement circuit board that I believe is in full working order and is available for resale at a heavy substantial discount from $300. LCP “Fixed It” , posted Thu 23 Jun 22:30 ______________________________________________________________________ Guess my “trusted” HVAC guy is an incompetent idiot. It took me about 10 minutes of actual “troubleshooting” to fix it. The culprit was a bad flame roll-out switch. A minute of looking at the wiring diagram showed where the flame roll-out circut is, and sure enough, one of the flame roll-out switches was sticking open. A minute with a multimeter was all it took. I bypassed it and everything immediately worked fine. Now I just need a new flame roll out switch, which looks like a very inexpensive part — maybe 1% of $300. Any suggestions on what to do about getting something from my HVAC guy to make up for the $300 I wasted on his misdiagnosis? He hasn’t returned my last page from this morning, although he knows from the other day a new circuit board didn’t fix it.

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