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

Worked out perfectly.

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 - ground Blue - Thermostat 24V Yellow - Pilot Valve White - Main Valve Brown - 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!

Replaced failed 20 year old control unit with this updated replacement. Easy install, worked fine. It took a little web research to be confident that it was the control unit that failed and not the safety switch or gas valve/regulator.

(video shows bad module before I replaced it with this new module) My 30+ year old Lennox 78UGF4-100-1 started making a loud clicking sound and wouldn't light. We called the repair man but of course it worked just fine while he was here. We basically paid $140.00 for the tech to say there are probably holes in the old wires (despite him testing wiring for continuity) and make a sales pitch for a new hvac. First if there are hole in the wires, which ones and why not replace them. Second, our previous house was built in 1959 and there weren't "holes" in the much older wiring. I initially tried cleaning the flame sensor and ignitor. The furnace fired up the 1st time but wouldn't ignite the second time. After replacing the flame sensor and the pilot assembly I had the same problem. I watched " Gas Furnace Spark Ignition Control Troubleshooting- Two Rod! " and " HVAC Service Call Bad Furnace Control Board / Spark Ignition " on Youtube and they helped me diagnose my problem. Turns out the module was sending an intermittent 12v pulse to the gas manifold (PV) instead of a steady 24v. Installing the new module was straight forward, however the order of the connections have changed from the original SP745 board. The module also doesn't have the screw mounts like the previous module. The new module comes with a 3m type foam mounting strip and two random screws. I'm not sure what the screws were for and used the mounting strip to mount in place of the old module. Hopefully it holds up. The new board also has the added benefit of a "LED Display" according to the mfr. website. It's really just a led bulb that blinks if there is a problem, but still better than nothing like the old module.

I only write reviews when I'm really impressed with something: This one fits the ticket. My ancient Lennox G16 Conservator III furnace had been acting up, with the inducer coming on, but the pilot not lighting. I replaced the Ignitor Module and Flame Sensor first, but no-go, so I ordered this as a replacement for the nearly 40-year-old Robertshaw SP735L Ignition Control Board (Absolutely amazed it lasted so long!). This unit required two new holes to be drilled and some longer screws than were furnished. I marked all wires before I removed them from the old board and re-installed on the new one. The LED came on steady green, and the furnaced fired right up after re-setting the thermostat. Please do NOT try this if you are not handy with a multimeter to make sure EVERYTHING is turned off. Lots of wires, lots of chances to get zapped if you don't have all power turned off (furnace, thermostat, etc.)

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.

Winter had arrived and my heater decided to start having an electronic hardware buzzing sound every time the thing cycled on. Sometimes it'd be brief and other times nearly a full minute long. I began a seemingly futile internet search for answers with almost all of the results mentioning either the blower or a loosely attached component to the blower as the culprits of buzzing noises. Both of which were nowhere near where my sound was coming from. I'm not going to try to promote somebody to start sticking their hands into their HVAC system without any research or even at all. But after ample research. Ample. I was able to diagnose my issue as the ignition module with certainty. Which I imagine you already have as well if you're sitting around reading reviews. After more research and narrowly avoiding buying an identical old stock part off that auction website, I finally found out about the Universal Robertshaw units. I found this one that would replace my LENNOX SP745(NR-C-60-30) unit. Make sure you've checked their website and cross reference charts. Prices are higher elsewhere and that's not including potential further markups and labor costs of hiring a professional. Which is definitely what you should do and I would still recommend. But buying it on my own at Amazon prices and cautiously replacing it on my own saved me a lot of money. Likely hundreds, with an S. The instructions and packaging are very minimal. If you need replacement sensors or wires you won't find them here. This is just the module, two screws, and a double-sided sticker mount. There is an assumption that you know what you're doing. Which again, you should. I am glad this was available on Amazon at this price though. Easy five stars.