Why Your RV Air Conditioner Isn't Cooling

It's ninety degrees, the AC is running, and the air coming out is barely cool. Before you call anybody, there are a few things worth ten minutes of your time.

Check these yourself

The filter. Pull the interior cover and look. A filter packed with dust chokes airflow, and low airflow feels exactly like low cooling. It's the most common cause we find and it costs nothing to fix.

The coils. Take the outside shroud off — usually a handful of screws — and look at the fins. Cottonwood, road grime, and bugs pack into them and the unit can't shed heat. They clean up with a soft brush and a gentle rinse. Don't bend the fins and don't hit them with a pressure washer.

Your power. This is the big one, and it's not really an AC problem. RV air conditioners need real voltage to run. At a crowded campground on a hot afternoon, park voltage sags. Below roughly 105 volts, your compressor is struggling and you're on your way to damaging it.

Get a voltage reading at the pedestal or from your monitor panel. If it's low, that's your answer, and running anyway is how compressors die. This is the reason a good surge protector with low-voltage cutoff is worth the money.

Your extension cord, if you're using one. An undersized cord on a 30-amp load drops voltage badly.

Return air path. Check that the return isn't blocked and that ducted units aren't leaking cool air into the ceiling cavity through a gap.

What needs a technician

The capacitor. If the fan spins but the compressor won't start, or you hear a click and a hum and nothing happens, a failed start capacitor is a very common cause. It's an inexpensive part. It also stores a charge that will hurt you, so this isn't a first-time DIY job.

Low refrigerant. RV rooftop units are sealed systems. They aren't designed to be recharged, and if the refrigerant is low, there's a leak. In most cases the economical answer is replacement, not repair, and anyone offering to top it off is selling you a temporary fix.

Compressor failure. Unit hums, breaker trips, nothing cools. Usually terminal.

Thermostat or control board. Especially on units with a wall thermostat talking to a roof board. Sometimes the AC is fine and the board isn't telling it to run.

Frozen coil. If you see ice, shut the compressor off and run the fan alone until it melts. Then figure out why — low airflow or low refrigerant, almost always.

Realistic expectations

An RV rooftop unit is generally rated to pull the interior down about 16 to 20 degrees below outside air. On a 95-degree day, 78 inside is the unit working correctly, not failing. Two units on a big fifth wheel help. Reflective window covers and closing off unused space help more than people expect.

We come to you

AC work is ideal mobile service — you don't need to move the RV, and we'd rather not have you towing a hot camper across the county in July. We service and replace rooftop units throughout our area, seven days a week during the season.

If you're already sweating, call early in the day. Summer heat waves fill our schedule fast.