Why Does My Evaporative Cooler Smell? Causes and Fixes

An evaporative cooler should blow fresh, slightly moist air. If it smells musty, swampy or fishy, the cause is nearly always water that’s been sitting too long, or something growing on the pads or in the tray. The good news is it’s usually easy to fix.

1. Stale water in the tray

Water that sits in the tray between uses goes stale, especially in warm weather. Most modern coolers drain the tray automatically after they turn off. If yours doesn’t, or the water sits for days, the drain or dump valve may have failed or been turned off. See dump valves vs drain valves and drain and dump valves.

2. Dirty or old pads

Pads that have collected dust, scale or algae can smell, especially when first wetted at the start of the day. Clean or replace them. See when to replace cooler pads.

3. Sludge in the tray

Leaves, dust and dead insects break down in the tray. Turn off the power and water, drain the tray and clean it out. Clean the pump inlet screen too.

4. New pads

New pads can have a slight smell for the first few days of use. This usually fades quickly. Running the cooler on cooling mode with windows open helps.

5. Low water flow over the pads

If the pump is weak or the distributor is partly blocked, the pads wet unevenly. Dry patches collect dust and salt, then smell when wetted. Check the pump and hoses. See how to replace a cooler pump.

6. Smell after winter

A cooler that’s been sitting all winter often smells at first start-up. Clean the tray, check the pads and flush fresh water through before the first hot day. See our spring start-up checklist.

Keep it fresh

• Run the cooler regularly in summer so the water keeps moving
• Make sure the tray drains when the cooler turns off
• Clean the tray and check the pads at least once a year
• Prepare the cooler properly for winter. See winter shutdown.

Popular replacement parts

• Breezair / Braemar Drain Valve and Shutoff 24VAC (105345)
• OEM Bonaire Dump Valve Drain Assembly Part No.6001336SP (6001336SP)
• Bonaire / Celair Aquamiser Dump Valve Kit (6051658SP)
• CoolBreeze Counterweight Drain Valve Kit #SP2040 (2001-2012) (SP2040)
• Breezair Chillcel Pads Pack of 4 – EM, ES, EX, EXD, EXQ, EXH (114613)
• Bonaire Filter Pads Celdek Medium VSM 60-65 (6050115SP)

This guide is general information only. Always follow your cooler manufacturer’s instructions, and use a licensed electrician for any electrical work.