Robertshaw 780-845 Ignition Module, Intermittent Pilot, 24V

Ran into a problem with our Lennox Whisper G20 last season where it would light, run for a few minutes, then go out before getting up to temperature. Then I took a air compressor with nozzle and blew out the heating element chamber and we were fine the rest of the winter. I didn't think much of it other than when the main burner would first come on, the furnace would making a strange clicking noise. I would assume to hear a clicking noise when igniting the pilot, not when opening the main valve.This year, the clicking noise got even worse. I assume it was the sound of the MAIN VALVE relay in the ignition control. Well, eventually, the house started getting cold and in investigating, found that the furnace would light the pilot, eventually kick on the blower motor, but the main burner never came on and the system would shut down right away. I cleaned the flame sensor rod, tested the flame sensor current (1.8 microamps), but none of those things helped. I found AC voltage when the pilot lit across PV & PV/MV, but never found any voltage across MV & PV/MV. It would never open the main valve (turn on the main burner). I assume the clicking relay in the Robertshaw SP 835 (that it was currently equipped with) finally gave out and that I needed to replace the control. I ordered this on Saturday and received it Tuesday (one-day shipping? My only gripe is that I think one day shipping should mean one day) and as soon as I hooked it up, the furnace worked perfectly. Interesting difference with this model is the tail for the flame sensor which allows you to bypass it. It can be bypassed by plugging the black wire directly into the sense spade. Please don't do this- I wish it weren't equipped with this feature. Make sure the flame sensor is plugged in and the tail (the black wire) is hanging not plugged into anything. Otherwise, it will think the burner is lit, even if lighting fails, and could fill your house with gas.Anyways, so far, so good. If I have any problem with it I will update the review.

My original Lennox furnace from 1990 stopped working and the HVAC repairman told me that my ignition board module is no longer working which is causing it to not sense the burning pilot flame thus not lighting the burners. I was quoted $500 to replace the board, fair or not, I didn't want to waste that kind of money on a furnace WAYYY past replacement life but money is very tight and I wanted to at least limp along until I can afford a new furnace. The model of my board is a Lennox SP745 and I've read that this 780-845 is the replacement for mine so I ordered it. I shut the power off to the furnace and swapped the board in 5-10 minutes. Very easy, just take note which color wire goes to what on the old board and then match it up to the new board. The only difference is that my old board had "IGN" for the spark wire and the new board had "SPARK" labeled for that. I turned it on, waited a few minutes and BAM, the burners lit and no more wearing a sweater and jacket inside the house! I will update if anything changes.**** UPDATE *****25 month update: Everything is still working! The only minor issue with my furnace now is that during heavy winter use the pilot light goes out once a week which then blows cold air. Luckily I just have to flip the breaker off for 10-20 seconds and the pilot re-ignites and blows warm again. I don't know if this ignition module is to blame or if it's something else on this ancient need to replace soon furnace.

I have an old Carrier 58gsc. It would start, sometimes, then stop. Wiggling the wires seemed to help so I decided the springs connector to the lockout/ignition controller LH33WZ512A had worn out. The 6-pin connector on the old controller looked hard to replace so I took a chance and ordered this controller with friendlier looking connectors. I used $7 worth of "disconnect" terminals that came with a crimping tool and it was within my capabilities.Installation notes: I didn't seem to need to hook everything up. 'PV/MV common' and 'Transformer ground' on the new controller were left floating.I connected the sense to the adjacent terminal on the controller as suggested by the instructions. From the old connector to the new controller:Black - groundBlue - Thermostat 24VYellow - Pilot ValveWhite - Main ValveBrown - No connection (This floats at 24V when the furnace is on. I think it has something to do with the old flame sensing mechanism but this controller doesn't seem to need it.)I was really pleased how quickly the furnace started up. Just a few seconds; much quicker than the old controller. Also, when I turned off the gas, the controller immediately locked out until I turned the thermostat down and back up again. Seems safe. Not sure how the flame sensing works; seems like magic; but works. At one point I connected the brown wire to PV which is wrong and the controller LED blinked then shut down which was helpful in guessing the connections.I had paid some con artist $90 to quote me $650 to replace the perfectly good control valve. This box fixed my problem for $80. Great product!