Rattling noise in Trane Furnace

[Mickey35]

I have a 3 year old Trane HAVC system. There is a rattling noise that is coming from inside the furance cabinet. I did not have the noise when it was on heat, but now in AC, the noise has appeared. Sotra souns like something lose. It is beyound me what it is - - if you can recommend what to look for it will be very much appericated. I hate to pay for a service call and the tech finds a small something that is not effecting the unit except for the noise and is not really a problem.

[HayZee518]

well, the fan works in both cases, a/c and heat so we can rule that out. the heater is a seperate section and it works ok on that mode so we can rule out that part. only thing left is the air conditioner compressor and/or condenser. check the copper lines coming off the compressor aren't hitting something also the condenser lines. maybe a clip came off allowing the tubing(s) to hit something or each other.

[Mickey35]

I thank You for the reply to the problem. I checked the furnance out - -nothing lose or missing. I do think (now)that the noise is coming from the air intake more than from the furnance. I hpoe you have some idea on what to look for. I have tapped on the inlet (16X20) from the inside and found nothing loose. The inlet is in the hallway celing just outside of the furnance room.

[HayZee518]

trunk lines are genrally "cross creased" when they make them. if one or two got by that process, the air pressure inside the trunk line will blow the sides out and then they retract when flow deminishes or the air flow is shut down.