whats inside there?

[jodil]

This is a furnace in a manufactured home. The thing that the arrow is pointed to is making a lot of unusual noises, what is that?

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[StevenT]

The answer you want is probably on the schematic in the picture, too small for me to see. Because of where it is and how it is wired, from here, I'd guess it's some sort of shut off safety switch. Perhaps it detects heat of spill back of fumes.

[John Dirks Jr]

My guess is, it is a pressure sensor that detects that the draft inducer fan is running. When it does this, it then allows the ignition process to continue.

I copied the following from an article;

On a signal from the room thermostat that heating is needed, the first thing that takes place is the draft inducer begins running and creating a draft in the heat exchanger. If there is no obstruction in the flue pipe of the furnace, the inducer will send a small pressure to the pressure switch via a small rubber tube, obviously, this tubing must be free of debris or any cracks. If there is sufficient draft, this will close contacts inside the pressure switch. The pressure switch then sends a signal down to the control board which is usually mounted in the blower section. There are various safety controls such as, but not limited to, over temperature limit switches, plenum thermostats, flame sensors, and roll out switches that must be closed, but if they are and the control board is good, a signal will be sent to the ignition device.

[belvedere]

agree w/ John

[Richard Saunders]

Hi all, I am a lurker that has decided to join the forum. The safety switch is above and to the left of the arrow. What you are pointing to is the manifold that is connected to the positive pressure switch. The gasket may be faulty and leaking pressure which may cause a whistling.