Have a Lennox G23 series gas furnace. Found another thread with exact issues I was having: 1) Furnace lights normally 2) Heater blower does not engage after the 45 second window 3) Furnace shuts off due to over-temp sensor triggering If the fan is set to "On" instead of "Auto", the furnace runs fine: If I have it set to "On" before engaging Heat, it'll shut the blower off for a few seconds, engage the ignition, then re-engage the blower Otherwise, if it's "Auto", I can still light the flame and just turn on blower to "On" before the over-temp kicks in. Based on that old thread, it looked like a Blower Controller needed replacing (BCC3 in my case), which I did, however it did not resolve the issue. So, I decided to step through the diagnostic test in the manual with a multimeter. Here is where I'm confused with the results: 1) Manual says if the flame is on, then after 45 seconds there should be 120VAC to the Heater blower -(N)eutral and (H)eat should have 120VAC - they did 2) If blower was not running, then I should check for 24VAC between "T" and "V" (Valve sensor and Common coming from Ignition Control) - they did So, both these results indicated I need to check the blower and blower wiring. Here's what I got when doing some further testing: 1) When just blower "On" without flame, I get 120V between N and "A" (Blower cooling tap - Black wire) - basically engaging blower at full speed, but also 167V between N and "H" (Heater - Red wire) 2) When flame is on but Auto blower doesn't engage, I get the 120V between N-H after 45 seconds 3) Turn Blower "On" with flame, I get 120V between N-A, and again get a high 167V between N-H 4) I then turn blower back onto "Auto" with flame lit, N-H stay at 167V, but N-A (which should disengage completely) stay at 120V 5) With flame turned off and blower going into the 90 second cooldown, N-H drop to 120V, N-A drops to 80VAC 6) In running the test a few times, it seems that occasionally the "Auto" will succeed in getting the blower running through H at 120VAC...but it lags for a few seconds after hearing the relay click at the 45 second mark. N-A do have the 80VAC on them though. [B]In summary:[/B] Blower does not engage with heat; Controller Board replacement did not resolve. Manually engaging blower prevents over-temp, but voltages are seemingly off. Whenever the blower is on, N-A seems to be at 65-75% the voltage of N-H. If I force it on, I get 120 at A and 167 at H; if H manages to do its thing at 120V, A still gets 80V. Given that my BCC board seems to be engaging at the right times, is this a case of the blower motor having a short/issue?

I have a York Diamond 80 HVAC (about 20 years old) System will start I get flame than randomly flame goes out. I watch it relight, will come back on system runs and flame goes out again. This is very random and sometimes if I just hit the emergency cut off and turn back on it will run fine. I have cleaned the flame sensor and made sure filter is fine I have checked and I do not get any error code. Looking for any suggestions