RobertShaw 780-715U

Old 02-25-08, 06:09 PM
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RobertShaw 780-715U

Hi Everyone,

I had an ignition problem on my Lennox heater for weeks. It would intermittently fail to ignite the pilot. Finally, a tech came by today and replaced the ignition module with a RobertShaw 780-715U. I think it's OK now except for one thing: when the furnace fires up, the ignitor continues to spark. I discovered that the flame sensor wire was disconnected from the module. So I called the tech to tell him about this and he said it's normal since the ignition module do not really require the flame sensor anymore. I would really want to believe what he said except that I want to verify from anyone that it is indeed OK that the module would continously send sparks while the heater is ON. Won't that cause anything to burn-out?

I looked at the ignition module and read from its side that it is factory-set for combined sensor/ignition wire. While it could take in a separate sensor wire, it says I have to remove the plug from the optional sensor terminal. Can anyone explain to me how this is done?

Thanks in advance for the help.
Old 02-26-08, 09:01 AM
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sparks should cease immediately once the pilot flame is present. We likely have here a case of miswiring of the module or poor grounding (or both).

Please post pictures (close-ups) of the control area (showing the module, pilot assembly, transformer, etc.) to help you further

Last edited by pflor; 02-26-08 at 11:05 AM.

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