I am going to have to leave. Going to opt out and let another expert answer the question Ris
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Can you get the full model # XXXXX the furnace? It will be on a tag inside the burner compartment accessible by removing top panel.
Okay, great. Now, before we go any further, you said there was water coming down the flu... is it coming inside or outside the flu?
Okay, I just want to make sure the water isn't getting inside the burners or on the electrical components.
Let's go ahead and clean the flame sensor (be sure to unplug furnace first). The tip will be directly in the flames and can be cleaned with steel wool (see pic below). Now, plug the furnace back in and check heat.