Generators that never get serviced are the ones that fail on the day you need them. We have written before about sizing a generator and about fall pre-storm prep. This post is the pre-summer version — the service routine we recommend in June or early July, before the July thunderstorm season starts hitting Ontario in earnest. Here is what we check, what fails most often, and the timing that matters.
Why pre-summer service matters more than spring service
Most customers who put a generator on a service plan default to spring service — once the snow clears, the unit gets the annual look-over. That is fine for cottages where the outage profile is dominated by winter ice and fall storms, and where the generator might run a half-dozen times between November and April.
For everyone else, the bigger outage risk is the summer thunderstorm season — late June through August, with July as the peak month. Heavy storms drop trees on lines, lightning strikes substations, and the grid takes hits faster than the utility can dispatch crews. A generator that did the spring service three months ago has had time to develop new issues: a battery that lost capacity in the heat, a fuel system that has a stale-fuel problem, an ATS that has not transferred since the last test cycle.
The pre-summer service is a second checkpoint, lighter than the spring annual, focused on the items most likely to have drifted since spring.
The battery: the single most common failure
The starting battery on a standby generator is what cranks the engine when the ATS calls for start. If the battery is weak, the unit either does not start or starts slowly and times out into a fault. Battery failure is by far the most common reason a generator fails to deliver during an outage event.
What we check in pre-summer:
- Voltage at rest. A healthy 12V starter battery sits at around 12.6V open-circuit. Anything below 12.4V is suspect.
- Voltage under crank load. Connect a load tester. Cranking voltage should hold above 9.6V. Below that, the battery is failing.
- Terminal corrosion. Any white or green corrosion on the terminals — clean, re-tension, apply terminal protectant. Corroded terminals cause start failures even on a good battery.
- Date code. Standby generator batteries last 3-5 years. A battery older than that, even if it tests okay in spring, is a candidate for proactive replacement before the storm season.
We carry replacement batteries on the service truck and swap on the spot if needed.
Oil and filters: between annual changes
The full oil-and-filter service is on the annual cadence (or after a specified number of run hours, whichever comes first). The pre-summer check is to verify the oil level, look for any signs of contamination, and check the filter for damage. If the unit has run significantly between scheduled services (extended grid outages can put a lot of run hours on a generator in a short window) the oil might be due for an off-cycle change.
The check on each:
- Oil level on the dipstick — should be between marks, leaning toward full
- Oil colour — fresh oil is amber, used oil darkens with hours but should not be black or opaque
- Oil smell — burnt smell or fuel smell is a flag
- Air filter — pull it, inspect, vacuum or replace if dirty
- Fuel filter (on diesel units) — drain water, check restriction
The exercise cycle: verifying it actually runs
Every standby generator is programmed to run a brief exercise cycle weekly or monthly: typically 10-15 minutes once a week, sometimes longer. The exercise runs the engine, circulates oil, and confirms the start-up sequence works. If the exercise is not running (which we have seen because of dead batteries, fault states the owner did not know about, programming changes after a firmware update) the generator has been sitting cold for weeks or months. That is the unit most likely to fail at the first real-event start request.
We verify the exercise:
- Read the controller history log — when was the last successful exercise cycle?
- Trigger a manual exercise if the unit supports it
- Listen for clean start, smooth idle, no smoke, no rough running
- Read the controller status after the cycle — any fault codes, any warnings, any pending alerts?
The automatic transfer switch: the part most often forgotten
The ATS senses utility loss, signals the generator to start, and transfers the load from utility to generator. The ATS has its own failure modes and they rarely show up in casual operation.
- Visual inspection. Open the cover. Look for any signs of arcing on the contacts, any discoloration, any insulation breakdown.
- Manual transfer test. Trigger a controlled transfer — utility off, generator picks up load, runs for several minutes, utility back on, transfers back. Watch the timing and the load pickup.
- Battery-back-up on the ATS controller. Some ATS units have their own coin or AA battery that keeps the controller alive when both utility and generator are off. End-of-life battery is a silent failure that surfaces during a real outage.
- Wiring termination torque. Both line-side and load-side terminations under the manufacturer-specified torque. Loose terminations on a high-current connection run hot and can fail under load.
Fuel system: propane and natural gas
For propane units, the fuel side has a few things we check:
- Propane tank level — owner is responsible for fills, but we note the level and recommend a fill if it is low going into the storm season
- Regulator condition — any visible damage, ice buildup from a recent test cycle, signs of leakage
- Fuel-line connections — none should be weeping, none should be visibly compromised
- Demand regulator pressure — gauges where the unit has them
For natural gas units, the gas-fitter scope is similar but the supply pressure under load is the key check — a natural gas service that has enough pressure at rest but sags under the generator's full-load draw causes hard-running or shutdown faults.
What we are watching for in 2027
The failure modes we have seen most often in 2026-2027 service visits:
- Battery failure — still the number-one reason a unit does not deliver during an event. The trend toward AGM batteries with longer service life helps, but they still age out.
- Exercise cycles that were silently disabled after a firmware update or a controller reset. We check the cycle log on every visit.
- ATS battery on the controller end-of-life. A handful of installs have had the ATS controller go dark mid-outage because its own backup battery had died.
- Cellular monitoring units with expired subscriptions. The cellular network behind the monitoring service has had several SIM-card transitions in recent years; some older units have been silently offline.
- Outdoor enclosure damage from rodents. Mice and squirrels nesting in the generator enclosure, chewing wiring harnesses. More common at cottages but not exclusive.
The annual cadence we recommend
For most residential and cottage customers, the cadence is:
- Annual service in spring — oil, filter, plug, full inspection, ATS test under load
- Pre-summer check in June or early July — battery, exercise verification, ATS controller, quick visual
- Pre-winter check in October or November — extended cold-start verification, propane sufficiency, transfer switch under conditions
Three visits a year on a managed unit costs less than one failure event. The math has been steady on that for the entire life of this company.
When to call us
If you have a standby generator and you have not had it looked at since the spring, get the pre-summer check on the calendar before mid-July. We do this work across Huntsville, Bracebridge, Gravenhurst, Port Carling, Baysville, and across the Golden Horseshoe. Request a generator service visit and we will get you on the schedule before the storm season hits.