26/10/2025
🫡 Ever wonder 💭 why you have those ugly streaks coming from your RV’s AC?
I think 🤔 I’ve found the answer. 💡
🟡 1. Rust or Corrosion Runoff
Inside the A/C’s metal base pan and coils, condensation collects and mixes with small amounts of rust or oxidation from the evaporator or mounting hardware.
When the water drains out onto the roof, it carries those rusty particles — leaving yellow, orange, or brown streaks on the rubber (EPDM/TPO) roof membrane.
Signs this is the cause:
• The stains appear mostly under the front or side drain area.
• The streaks fade out after a few feet.
• You may see rust spots on the pan when the shroud is removed.
🧴 2. Plasticizer or UV Breakdown from the A/C Cover
The white shroud (the outer plastic housing) can degrade in the sun and heat, leaching out chemicals or “plasticizers.”
These can run off with condensation or rainwater and cause yellow or tan streaks that look oily or waxy.
Signs this is the cause:
• The stains are the same shade as the cover or slightly darker.
• They return after cleaning, especially in hot weather.
• The shroud feels chalky or brittle (a sign it’s aging).
💧 3. Condensate Drain Path Contamination
If the A/C has a drain kit or internal drip pan, algae or mildew can form in the line, producing yellowish biofilm that seeps onto the roof.
Signs this is the cause:
• There’s a faint musty odor.
• The runoff is slimy rather than rusty.
• You may notice water dripping in unusual places.
🧽 4. How to Clean It Safely
1. Use a non-abrasive RV roof cleaner or a mild mix of:
• 1 part hydrogen peroxide or white vinegar
• 3 parts warm water
2. Scrub gently with a soft brush or Magic Eraser pad.
3. Rinse thoroughly and avoid strong solvents like acetone, which can damage roof coatings.
4. For stubborn rust-based stains, try Bar Keepers Friend Soft Cleanser (the liquid kind), used gently.
🧰 5. Prevention Tips
• Inspect and clean under the A/C shroud every 6–12 months.
• Repaint or replace any rusted metal base parts.
• Replace aging shrouds (especially if over 5 years old).
• Install drain diverters to channel condensate away from visible roof areas.
Or call me at 813-659-0008 ext 10529 to schedule your AC Service and Inspection 🧐 at Blue Compass RV in Tampa (Dover) FL.
