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Can you give me model on furnace? Does anything come on> Do you have a volt meter for troubleshooting?
Is this gray box inside the furnace or is it a condensate pump that sits beside furnace to pump condensate outside?
I am not familiar with this box that would be humming.If trap were clogged up furnace would not work.I am going to open to my colleagues to see if they have ideas.
Hello, before we start let me tell you that I do not have the faintest idea why you are hearing any buzzing from the gray plastic box.
However I have seen situations where noise can seem to be coming from one place but is actually coming from another.
If you like we can do some tests to help sort out what on earth might be going on.
First test is a push test..use a screw driver to press on various parts of the box and surroundings when you hear the buzzing.. tell me if you can get a change in the sound.. this will very often isolate a bad connection or vibrating piece of sheet metal.
If that fails, remove one of the wires that go into the box as a brief test, those would be for the liquid sensor, if the buzzing stops instantly we can figure that the sensor tip is arcing electric current to the condensate in the bottom of the box (that is an semi educated guess after 55 years in the business however.)
Let me know what you can find, we can go from there.
Hello again, unplug the furnace, try cleaning sediment from the box again, and look for a pair of metal probes with two wires attached (water level sensor) and clean those with emery cloth, try it again, let me know how it goes.
We can go from there without a time limit. If that solves the problem please do not forget to rate my service, it is how I earn a living and will not increase your charges.