The Day a Dirty Coil Sent Pressures Through the Roof
I got a call the other day from a homeowner whose AC “just wasn’t cooling.” Pretty common this time of year. When I arrived, the first thing I noticed was the refrigerant line going into the house—it was scalding hot, hotter than you’d ever expect to see, over 150 degrees.
I hooked up my gauges, and the numbers told the same story: the suction pressure was way up around 240, and the liquid line was pegged at 760 psi. That’s extremely high—far beyond where a healthy system should run.
Now, in cases like this, you could start thinking the compressor’s done for, or the refrigerant charge is wrong. But after digging a little deeper, I found the culprit: the condenser coil was absolutely packed with fine dust. From the outside it looked normal—nothing you’d notice with a quick glance—but once I washed it out, the system calmed right down. Pressures returned to normal, the refrigerant line cooled to the touch, and the house started cooling again.
The Important Takeaway
Here’s the part I really want homeowners to understand: this situation was dangerous. With the high-pressure sensor failing, the AC was pulling far more amps than it was rated to pull. Given time, it could start an actual fire as the wires overheat. Now the AC has to be overhauled to ensure this doesn’t happen again. Modern AC units have high-pressure sensors that are supposed to shut things down before pressures reach those dangerous levels. But sensors can fail. If you ignore warning signs—like the system running but not cooling, or lines that are hotter than they should be—you’re gambling with the health of the compressor. And that’s the most expensive part of the system.
What You Can Do
- Keep your outdoor coil clean—hosing it down gently once in the springtime goes a long way.
- Pay attention to how your system feels and sounds. If something seems off, call sooner rather than later.
- Don’t assume safety sensors will always save the day—they’re a backup, not a guarantee.
Catching this problem early saved my client from what could have been a very costly repair. A little bit of attention and maintenance can do the same for you.