Loud clicking sounds heard when the furnace is on

[westernviews]

There are loud clunking or clicking sounds heard at both ends of my Airstream connected to furnace activity, especially it's going on or off, that seem to have increased in volume this fall. I have assumed it is some part of the propane system. Have wondered if this is a sign that some parts need to be replaced or serviced. I worry the system will break down in a cold spell and cause the pipes to freeze.

Can anyone enlighten me on what these sounds are? I am currently traveling in South Texas and not near an Airstream dealer.

[HowieE]

My first thought, since it is continues, is the fan blade is striking the case. There is no reason to go to an Airstream dealer, any RV shop should be able to work on the heater.

If the sound starts as soon as the fan come on that would confirm it to be in the fan since the gas valve dose not open for about 15 seconds after the fan start thus eliminating any parts relating to the gas system or the heat exchanger.

[Jammer]

It may be something as simple as a leaf or piece of paper caught in the blower wheel.

[samb]

Sounds to me that it is from the duct system. You say "connected to furnace activity, especially, it's going on or off". At start-up and shut-down the duct system goes through the greatest heat changes and expansion and contraction. This quite often causes motion in the ducts resulting in "clunking" noises. When the system has warmed up to operating temperatures the noises usually quit, only to start again when cooling at shut-down. Does this describe your noises?
Sam

[Aage]

Mud-dauber nest?

[westernviews]

Originally Posted by samb

Sounds to me that it is from the duct system. You say "connected to furnace activity, especially, it's going on or off". At start-up and shut-down the duct system goes through the greatest heat changes and expansion and contraction. This quite often causes motion in the ducts resulting in "clunking" noises. When the system has warmed up to operating temperatures the noises usually quit, only to start again when cooling at shut-down. Does this describe your noises?
Sam

If I'm lucky, it is just duct expansion and contraction sound. It is not a continuous noise, just related to the furnace turning on or off.

Thanks all.

[HowieE]

Originally Posted by westernviews

If I'm lucky, it is just duct expansion and contraction sound. It is not a continuous noise, just related to the furnace turning on or off.
Thanks all.

The duct work is soft plastic tubing so I doubt it is that.

Again I would look at the fan. The fan shaft may move in or out of the motor housing during start up and shut down causing it to hit some thing at those times. Also the sail switch housing on the fan may be loose.