A year ago we wrote a generator fall prep post that covered the basics — oil, filters, battery, exercise cycle. That advice still holds and we are not going to re-publish it. This year's version is a debrief on what we actually saw fail on residential and cottage generators across Muskoka and the Golden Horseshoe in 2027, and what we have changed about how we service them as a result. If you own a standby generator, this is the version of the fall service conversation we are having right now.
The dominant failure mode this year: ATS communication
We service Generac, Kohler, and Cummins across both regions, and 2027 had a clear pattern: automatic transfer switch communication faults were the most common service call we ran. Not the generator itself — the ATS losing its conversation with the controller. Specifically:
- Generac Guardian units with the Mobile Link cellular modem dropping connection after a controller firmware update mid-summer. Units still ran on exercise cycles but the homeowner app showed offline. A handful needed a full controller reflash to recover.
- Kohler RDC2 control panels showing intermittent ATS-controller faults during exercise cycles. Root cause turned out to be a low-voltage signal wire that had degraded at a crimp where it ran outside the generator enclosure. Crimp replacement fixed every one we looked at.
- Cummins ATS units on commercial installs not transitioning back to utility cleanly after a long outage. Programming issue, not a hardware failure, but the unit would stay on generator power until manually reset.
What we changed: ATS firmware verification is now a documented part of every annual service. We pull the version, compare it against the current factory release, and update if needed (with the manufacturer's tool, not over-the-air for installs that have had issues with that). We also flex every external signal wire visually for crimp degradation.
Battery failures, on schedule
Generator batteries continue to be the single most predictable failure point. The pattern remains: 3-4 year service life on the OEM lead-acid battery, 5-6 years on a properly maintained AGM upgrade. What was different this year:
- We saw a higher rate of battery failures on units that lost utility power for extended periods in winter 2026-27. The battery powers the cranking system; sustained generator operation depletes the engine-driven charging system's ability to fully recover the battery; a few cycles of deep discharge later, the battery is done.
- Smart battery tenders integrated into newer controllers help but do not eliminate this. Worth checking the tender output voltage on annual service.
Fuel system issues we did not see in 2026
Two new patterns:
- Propane regulator icing on extended runs. A handful of cottage installs ran for 36+ hour stretches during the February cold snap, and we saw regulator icing on installs where the regulator was undersized or poorly insulated. Generator would surge, run lean, and on a few installs shut down on low fuel pressure mid-outage. The fix is a properly sized two-stage regulator and an insulated tank line. Worth checking on your install if you have not had a long run on the unit.
- Natural gas pressure droop on shared services. Two Burlington and Hamilton installs in 2027 had natural gas pressure droop when neighbouring properties were also running gas-heavy load. Generator did not get full BTU and would surge under load. Utility coordination resolved it (increased gas service capacity at the meter) but the diagnosis took longer than it should have.
The exercise-cycle issue that owners do not notice
Most generators are programmed to exercise weekly. The exercise is short (5-10 minutes) and the homeowner hears it but does not check it. What we found on annual service this year: a meaningful number of units were running their exercise cycle but NOT actually transferring to generator power. The exercise was happening with the ATS staying on utility. The engine was running. The generator was producing power into an open circuit. Nothing was actually being tested.
Why this matters: the exercise's whole purpose is to verify the transfer switch works. If the exercise does not actually transfer, you are not testing the part that fails on outage day. We now configure exercise cycles to transfer for at least 30 seconds, and we verify the transfer on annual service by watching the ATS contactor pull in.
What we are doing differently in 2027 service
Refreshed annual service scope as a result of this year's findings:
- Oil and oil filter change to manufacturer schedule. No change.
- Air filter inspection and replacement. No change.
- Spark plug inspection. No change.
- Battery test under load with a proper carbon-pile or electronic load tester, not just an open-circuit voltage check. Carbon-pile reveals the marginal batteries that pass open-circuit but fail under cranking load.
- ATS firmware version check and update. New this year. Documented on the service record.
- Exercise cycle transfer verification. New this year. We watch the ATS transfer during the next scheduled exercise.
- External wiring inspection at every crimp and termination point outside the generator enclosure. Flex every wire, look for green corrosion, retorque where accessible.
- Propane regulator and gas line inspection if applicable. Pressure-test under load.
- Transfer switch test under live conditions (controlled grid drop to verify start-and-transfer behaviour end to end).
What we still tell every cottage owner
The conversation from last year's standby generator sizing post has not changed. Right-sized 14-22 kW Generac, Kohler, or Cummins. Properly sized propane tank — minimum 500 USWG for cottages. ATS matched to the generator brand. Annual service non-negotiable. The brands all work; what kills generators is neglect and what saves them is a calendar reminder.
The fall scheduling window
September is the right month to book the annual service. By mid-October the calendar fills up with first-storm calls — generators that have not run all summer, owners discovering they will not start when they finally need them, and panicked schedules. Routine service in September goes on the calendar at our pace; service in October is reactive and the day will not be as flexible.
When to call us
If you have a standby generator and have not had it serviced this year, we cover Huntsville, Bracebridge, Gravenhurst, Port Carling, and Baysville for cottage work, and run the same service across the Golden Horseshoe. Book a service visit and we will get the unit ready for storm season. We service every brand we install and a few that we do not.