Parking AC Water Leakage Inside the Cab: Causes and Fixes

• Table of Contents

1. Cause 1: blocked condensate drain (most common)
2. Cause 2: gasket uneven compression
3. Cause 3: roof cutout seal failure (post-install)
4. Cause 4: split-unit refrigerant line ingress

Water dripping inside the cab from a rooftop parking AC is almost always one of three things: blocked condensate drain, gasket compression issue, or roof seal failure. Refrigerant leaks are extremely rare and not the first cause to chase.

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.

Cause 1: blocked condensate drain (most common)

A rooftop AC produces 0.5 to 1.5 liters of condensate per cooling hour. The drain holes on each corner of the unit must remain clear. Bugs, road debris and dust can block them within one season.

Fix: climb on the roof, locate the four corner drain holes on the unit base, clear with a small wire or compressed air. Run the AC for 30 minutes and re-check.

Cause 2: gasket uneven compression

If the four mounting bolts are torqued unevenly, the foam gasket between the unit and the roof cutout compresses on one side only — water tracks under the gasket on the high side and into the cab.

Fix: loosen all four bolts, re-seat the gasket flat, re-torque diagonally (FL → BR → FR → BL) to spec.

Cause 3: roof cutout seal failure (post-install)

If the installer used the wrong sealant (silicone instead of butyl tape) it can fail in UV and heat after 12–24 months. Water tracks around the cutout perimeter.

Fix: remove the unit, scrape old sealant, apply butyl tape gasket (Vethy ships replacement kits — see gasket install guide, coming soon), re-fit.

Cause 4: split-unit refrigerant line ingress

On VX3000SP split units, water can track along the refrigerant lines into the cab through the cable port. Confirm the port is sealed with the supplied grommet + butyl.

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

Could it be a refrigerant leak?

Extremely unlikely. Refrigerant leaks present as low cooling + E5 error, not dripping water.

How much water is normal under the truck?

A rooftop AC drips 0.5 to 1.5 liters per cooling hour onto the roof and down the cab sides. This is condensate, not a leak.

My unit only leaks in heavy rain — what's wrong?

Roof cutout seal failure. Re-bed the gasket with fresh butyl tape.

Do you ship replacement gasket kits?

Yes — standard kit includes butyl tape, foam gasket and replacement bolt set. See <a href="/parking-air-conditioner-spare-parts.html">spare parts catalogue</a>.