A typical Highland call comes from a cottage owner opening the place for fall weekends. The thermostat calls, and nothing happens. We ask a few questions on the phone first: is the gas on, is the power switch by the basement door on, and does the sight glass show water. Those three answers often save a trip, especially at this distance.
On this one, the switch was on and the gas was on, but the sight glass was almost empty. The water feed valve had been shut for the summer and never reopened, and the low water cutoff did its job by locking out the burner. That is good news. A cutoff that works is exactly what keeps a dry boiler from cracking.
Before refilling, we looked for leaks around the sections, the returns and the boiler drain. Nothing obvious. We filled slowly to about two thirds on the glass, then ran a blowdown on the cutoff to check that the float moved freely. The water came out brown at first, so we flushed until it ran clear, skimmed the surface and confirmed the burner shut off on the test.
Then we fired it. The standing pilot lit, the main burner came up clean, and the pressuretrol cut out under 2 psi. We walked the cottage, checked every radiator vent, and replaced one that would not close. Before leaving, we tagged the water feed valve and the gas valve, and wrote a short opening and closing checklist for the owner.