Ice on the line at a Lake Broward house in July: the myth that it 'just needs gas,' and the checklist that beats it

The myth first

Around the lakes and along the river you will hear it from well-meaning neighbors: ice on the line means the system is low on gas, and all it needs is a top-off. Sometimes low refrigerant is the cause. Even then, “a top-off” is the wrong fix, because the refrigerant went somewhere, and the leak that let it out is still there. More often, in Putnam County, the cause is not refrigerant at all. It is air.

An evaporator coil freezes when its surface drops below 32 degrees, and that happens when there is too little warm air moving across it to keep it above freezing, or too little refrigerant to keep the pressure where it belongs. A system can be perfectly charged and freeze solid behind a clogged filter. A system can have a clean filter and freeze from a slow leak. The checklist below sorts them.

The homeowner checklist, in order

1. Turn the thermostat from Cool to Off, and the fan from Auto to On. Warm indoor air across the coil melts the ice without stressing the compressor. Nothing else can be checked until it thaws.
2. Pull the filter. Hold it to a window. If light does not pass through, you have likely found the cause. A Palatka filter after a pollen spring, or in a house near the mill or the potato fields, can be solid in three weeks.
3. Look at every supply register and the return grille. Furniture against the return, closed registers in unused rooms, a rug over a floor return in an old frame house: all of these starve the coil.
4. Check the outdoor unit. Is the fan turning? Is the coil caked with cottonwood fluff, grass clippings or pollen? A dirty outdoor coil is a less common freeze cause but a common efficiency one.
5. Put a towel down. Melting ice overflows the drain pan. In a hall closet on a wood floor, that matters.

When to stop and call

Stop when the filter was clean and the registers were open and the coil still froze. Stop when it has frozen more than once this season. Stop if the ice came with a hissing sound at the handler, or if the system has been losing ground on hot afternoons for weeks. Those point to refrigerant or a failing blower, and neither is a homeowner repair.

Also stop if the air handler sits over a finished space or in a closet with a wood floor, because the thaw itself can do water damage, and we would rather be there for it.

Call about a frozen coil

What we do when we arrive

By the time the truck gets to Pomona Park or Satsuma from the Palm Coast headquarters, the coil has usually thawed. We confirm airflow first: filter, blower speed and condition, static pressure across the coil, duct restrictions. If the coil itself is matted with dust that bypassed a bad filter, it gets cleaned. Then the refrigerant side: pressures and temperatures on both lines, and if the charge is low, a leak search rather than a top-off. On a system on an old refrigerant with a leaking coil, you get a straight conversation about repair against replacement, with numbers.

Finally the drain. A frozen coil floods the pan when it thaws, and a drain line already scaled with iron and sulfur from Putnam well water may not carry it away. We flush it and make sure the float switch works.

Keeping it from freezing again

Change the filter on a schedule the house actually needs, which in a Palatka spring may be every three weeks for a one-inch filter, or upgrade to a media cabinet that goes months. Keep registers open. Have the charge checked at the spring tune-up, before the long season starts in mid-May. A coil that froze once is a coil asking for maintenance; a coil that freezes every summer is a system with a leak that needs finding.

No after-hours charge, any day, from the shop 35 miles east.