Troubleshooting Buzzing in the Trane Rooftop Supply Fan

Root of the Buzzing

• Simply put, the buzzing noise you’re hearing is essentially a high-speed rattling that’s typically caused by two or more components rubbing against one another during a heating or cooling cycle. There are several working bits that go into a Trane unit’s construction, but generally the buzzing noise will emanate from a few known culprits: the duct work, condensers, fan or relay. By systematically checking each, you should be able to narrow down the list and pinpoint the underlying problem.

Duct Work

• Vibration caused by the central air unit powering up or down prior to or after a cycle will reverberate throughout the duct work. If one of the rooftop ducts leading into the structure isn’t securely braced, buzzing or rattling will surely result. The easiest way to determine if the duct work is the cause is to visually inspect the braces along the ducts and to secure any that are loose; if none is, find flat spots midway between the joints on the metal itself and create small indentations. This takes up “slack” and makes the ducts more rigid, thus eliminating or severely reducing the buzzing.

Condensers and Fan

• Condensers chill the air before it’s blown into the home or business via the fan, which is part of the blower assembly. Accessing these two components is a bit more involved, so if you’re uncomfortable with performing such work, this circumstance would warrant a call to a technician. Still, a quick check of the unit’s manual will diagram the location of these components. After removing the access panels with a screwdriver, gently shake each coil and the fan; if they shift in the slightest, tighten the holding bolts with an appropriately sized socket wrench.

The Relay

• The relay’s job in the air conditioner unit is to relay the signal from the sensor to the rest of the system. The relay is fairly small and is mounted onto the unit’s main control board. If the relay has been poorly seated, the vibration from the unit may be causing the unseated relay to vibrate the board, which in turns vibrates another component. If you don’t have electronics experience, you’d the need the help of a licensed Trane technician to seat the relay back onto the board.