Parking AC Noise Problem: Vibration, Buzzing and Whine Fixes

• Table of Contents

1. Rattle / vibration on rough road
2. Buzzing at low fan speed
3. Fan whine or scraping
4. Compressor knock at startup

Vethy parking ACs run at <49 dB(A) night mode at the bunk position. If the unit is noticeably louder than that, something is mechanically off — mounting, gasket, fan or compressor mount. This page covers the four most common noise complaints and the field fixes.

This page is a generic field troubleshooting guide for Vethy 12V/24V parking air conditioners. Always disconnect the battery before opening the unit and follow the install manual that shipped with your specific model. Refrigerant work (R410A) must be performed by a certified technician.

Rattle / vibration on rough road

Almost always loose roof mounting bolts. Torque the four corner bolts to spec (typically 8–10 N·m). Check that the foam gasket is evenly compressed — uneven compression transmits cab flex into the unit body.

Buzzing at low fan speed

BLDC fan motor PWM at very low duty can produce a 2–4 kHz buzz audible in a quiet cab. Step the fan one speed higher or switch to night-eco mode (smoothed PWM profile).

Fan whine or scraping

Indicates fan blade contact with the housing. Open the unit, check for ice buildup (in heat-pump models) or foreign object. If the blade is bent from road debris, replace the fan assembly.

Compressor knock at startup

A single startup knock is normal (compressor inertia). Repeated knocking under load indicates loose compressor mount or low refrigerant pressure — call a certified tech.

If the problem persists after the steps above, contact Vethy support with the unit serial number, install year and a short video of the symptom: info@vethy.com · Open a support ticket.

Frequently asked questions

My unit got louder after 2 years — what changed?

Most often the gasket has compressed unevenly and the mounting bolts loosened. Re-torque and re-seat the gasket.

Is BLDC fan buzz normal?

A faint hum is normal; an audible buzz is a PWM duty issue — change fan speed or update firmware if available.

How loud should it be in night mode?

Spec is &lt;49 dB(A) at the bunk position. Closer to the unit (under the roof) you may hear 55–60 dB(A) which is still normal.

Does adding insulation help?

Yes — a sound-deadening mat under the headliner around the unit can reduce perceived noise by 3–5 dB(A).