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Top 5 Tips for Winter Generator Maintenance

Why Winter Generator Maintenance Is Critical

When temperatures drop and the likelihood of wind, rain, and snow increases, so does the risk of power outages. This is when your backup power solution needs to truly shine, springing into action to maintain business continuity and prevent costly downtime.

To ensure optimal reliability when you need it most, every backup power generator should be covered by a scheduled servicing agreement carried out by our trained engineers. However, you can also perform several essential winter maintenance checks yourself between service visits to protect against freezing conditions and ensure your backup power solution remains ready to perform.

Winter generator maintenance is pivotal to ensure business as usual during a power outage.

Many of these checks form part of standard weekly inspections, but harsh winters and extreme weather conditions make them especially important.

👉 Need expert support? Speak to our maintenance team about preparing your generator for winter.

1. Canopy and Doors – Protecting Your Generator from Winter Damage

Often overlooked, the physical protection of your generator set can be critical during colder, harsher weather. Inspect the canopy for corrosion and ensure all doors and locks operate smoothly.

Winter brings increased moisture, rain, and snow, along with frequent use of de-icing salt — all of which accelerate corrosion on metal surfaces. If the canopy becomes compromised, water ingress can quickly damage sensitive internal components.

Freezing moisture can also cause locks and hinges to seize. If doors cannot be secured, the generator becomes exposed to the elements and vulnerable to tampering or part theft.

👉 Not sure what you’re seeing? Our engineers are happy to advise.

Action Tip: Clean minor rust spots and apply an anti-corrosion primer. Use a graphite lubricant on locks and hinges before the first deep frost.

2. Battery Health & Charger – Preventing Cold Start Failures

When the mains power supply is lost, your backup generator must start immediately. Battery failure is the most common cause of a generator failing to start in cold weather.

Low temperatures reduce cranking power and the battery’s ability to hold a charge. If sufficient current cannot be delivered, the generator simply won’t start when it’s needed most.

Using the generator controller, check the battery voltage. A healthy 12V battery should read ~12.6V or higher. Readings below 12.4V warrant investigation.

Battery condition also provides insight into charger health. Standby generators rely on a trickle charger to keep batteries topped up. If the charger fails, gradual discharge is almost guaranteed.

Action Tip: Inspect terminals and cables for corrosion or dirt. Clean with a stiff brush and baking soda solution, then apply protective terminal grease.

A working charger should show 13.2–13.6V on a 12V system. Lower readings or charger alarms indicate the battery isn’t receiving adequate support.

Engineer Insight: In cold conditions, batteries often pass visual inspection but fail under load. A battery that appears acceptable at rest can still collapse during cranking, particularly after prolonged standby. This is why winter failures often occur without prior warning.

👉 Concerned about battery or charger performance? Contact our team to investigate before winter outages occur.

3. Coolant & Engine Oil Checks for Winter Generator Maintenance

Correct fluid levels and antifreeze concentration are your primary defence against catastrophic engine damage during freezing conditions.

Coolant & Antifreeze – Preventing Freeze Damage

Coolant prevents overheating, while antifreeze stops the liquid from freezing. If the antifreeze concentration is too weak, the coolant can freeze, expand, and crack components such as:

  • Engine block
  • Radiator
  • Hoses

Action Tip: Never top up with plain water. It dilutes antifreeze and dramatically raises the freezing point while introducing impurities into the coolant system.

So, why does this matter? Freeze-related engine damage typically isn’t immediately obvious. Cracks can worsen over repeated start attempts, leading to progressive coolant loss and eventual engine failure — often during a live outage.

These failures are far more costly than routine maintenance.

Check that the expansion tank level sits between the minimum and maximum markings. Persistently low levels may indicate a leak and should be investigated.

Test the antifreeze concentration using a hydrometer or refractometer. A 50:50 or 60:40 mix is standard and vital for winter protection. Antifreeze also raises the boiling point and provides corrosion protection.

Antifreeze contains corrosion inhibitors that protect the engine’s internal metal components; however, these additives degrade over time. We recommend that coolant be replaced every 3 years —  this can be included as part of our Shenton Group maintenance contracts.

Engine Oil and Winter Cold Start Stress

Most generators require specific oil grades such as 10W-30 or 15W-40. Lower “W” numbers improve the cold-weather flow.

Cold temperatures thicken engine oil, increasing resistance during start-up. Old, degraded, or low oil significantly increases the risk of cold-start failure.

Check the dipstick level and oil condition. Sludgy, milky, or gritty oil indicates contamination and requires replacement. Standby generators should receive annual minor and major services, including oil and filter changes.

Action Tip: If you notice oil leaks, burnt smells or abnormal consumption, contact our engineers early — small issues escalate quickly in winter.

4. Fuel System & Engine Heaters – Avoiding Winter No-Start Scenarios

Cold weather exposes weaknesses in fuel systems. A few simple checks can prevent common winter no-start issues.

Winter Fuel Problems – Condensation, Microbial Growth & Diesel Thickening

Partially filled tanks allow condensation to form as moist air cools inside the tank. Water collects at the bottom, leading to:

  • Corrosion
  • Microbial growth
  • Freezing fuel lines
  • Restricted fuel flow

Keeping tanks well-filled reduces moisture formation. Long-stored diesel should be conditioned or polished — fuel polishing is a service provided by our engineers.

Inspect hoses for cracking or leaks. Diesel can also thicken in cold weather, causing:

  • Sluggish running
  • Delayed pick-up
  • Low fuel pressure alarms
  • Filter restriction warnings
👉 If symptoms appear, contact us to inspect filters and fuel condition.

SCR / AdBlue in Winter – Preventing Freezing and System Faults

AdBlue freezes at approximately –11°C.

If frozen:

  • ❌ Do not add water
  • ❌ Do not apply direct heat
  • ✅ Allow it to thaw naturally

Some systems include heated tanks or lines — check controller readings and breakers. After thawing, wipe away crystallised deposits.

Action Tip: Avoid filling tanks completely as AdBlue can expand by ~7% when frozen, which can cause damage.

Coolant Heaters & Sump Heaters – Ensuring Reliable Winter Starting

Coolant heaters keep engines warm, reducing cold start stress. Sump heaters maintain oil fluidity.

A standby-ready engine should feel slightly warm on safe external areas.

Signs of heater issues include:

  • Slow cranking
  • Laboured starts
  • Low oil pressure warnings
  • Cold engine after long standby
👉 If heaters aren’t operating correctly, contact our team to investigate.

5. Controls, AUTO Mode & ATS – Ensuring Your Generator Responds During Outages

After your generator has spent countless hours in idle standby, control system readiness is equally as important as mechanical checks and is central to standby generator winter preparation.

Why AUTO Mode is Critical in Winter

Ensure the Generator Controller is set to AUTO — not OFF or MANUAL. AUTO enables the controller to detect a mains failure and start the engine autonomously.

Alarms and Warnings That Prevent Load Acceptance

Check for active alarms. Even seemingly “minor” warnings can prevent load acceptance and cause unexpected ATS switching problems.

Remote Monitoring – 24/7 Visibility Without Being On Site

During winter, generators often fail when no one is present to spot early warning signs. Remote monitoring provides real-time visibility of generator status, alarms and performance.

Parameters such as battery voltage, heater operation, fuel levels, controller status, and active faults can be monitored remotely — providing reassurance during storms, overnight, or holiday periods.

For critical or unmanned sites, remote monitoring enables faster engineer response and proactive intervention, significantly reducing downtime risk.

👉 Learn more about our Remote Monitoring service

Automatic Transfer Switch (ATS) Checks

If your set includes an ATS or a changeover panel, you should ensure:

  • ATS is set to AUTO
  • No active faults found

If it’s isolated or in manual, the generator may start, but it won’t actually power your building.

Output Breaker & Emergency Stop Check

Confirm:

  • Output breaker closed
  • All E-Stops reset

Winter clothing and equipment can accidentally activate E-Stops, especially if they’re on plant-room walls or near doors.

Generator installation on an icy day.

Action Tip: After any maintenance or testing, perform a 30-second readiness sweep to prevent costly generator downtime – controller in AUTO, no alarms, ATS in AUTO, E-Stops reset, and breaker in the correct position.

Final Thoughts – Stay One Step Ahead This Winter

Winter places additional strain on standby power systems, and outages often occur when conditions are at their worst. While professional servicing is essential, these winter checks are critical to ensuring reliable performance.

By addressing small issues early, you significantly reduce the risk of no-start scenarios, emergency callouts, and costly downtime.

From routine servicing and winter health checks to fuel management, heater inspections and emergency response cover, our team is here to help.

👉 Contact our team today to arrange a winter inspection or discuss a tailored maintenance contract.

For added peace of mind, our remote monitoring solutions provide continuous oversight of your critical power systems, enabling early fault detection and faster response — particularly valuable during severe winter weather and out-of-hours periods.

For information on HV & LV Switchgear, UPS and CHP maintenance support services, please visit these dedicated pages.

Winter Generator FAQs