The block heater and jacket water heater work together to keep the engine warm while the generator is offline. The block heater warms critical engine components directly while the jacket water heater circulates heated coolant throughout the engine. Together, they maintain proper engine temperature so oil flows correctly and the engine can reach starting speed quickly.

• Direct Component Heating: The block heater maintains temperature in the engine block, keeping metal components above ambient temperature to reduce thermal stress during cold starts.

• Oil Viscosity Management: By keeping the engine warm, heaters maintain proper oil viscosity ensuring adequate lubrication is available immediately when the starter engages.

When these heaters fail, the engine starts cold. Cold starts increase internal friction, slow cranking speed, delay oil circulation and place additional load on the starter and batteries. On larger engines, a failed jacket water heater can lead to extended crank times or no-start conditions in cold weather. Repeated cold starts accelerate wear and shorten engine life.

How often should it be inspected?

How often should block heaters be replaced?

Heaters are checked during quarterly PM1 inspections for electrical draw, proper operation and actual temperature increase—not just whether the engine eventually starts. We measure heater amperage and engine temperature to verify proper function.

Environmental Considerations: In cold climates block heaters are critical for reliable starting. Heaters in regions with mild winters may receive less attention but still prevent unnecessary cold-start wear. Heaters exposed to moisture or corrosive environments require frequent inspection of electrical connections to prevent circuit failures.

• Extended Cranking Time: Engine takes longer than normal to reach starting RPM especially in cold weather indicating heater is not maintaining engine temperature.
• Engine Block Cold to Touch: Engine feels cold even after sitting on standby with utility power available suggesting heater has failed.
• Increased Battery Load During Start: Batteries strain more than usual during cranking as cold thick oil increases starting resistance.
• Low Oil Pressure on Startup: Oil pressure takes longer to build after start indicating cold thick oil is not flowing properly.
• No Current Draw at Heater: Measuring heater circuit shows zero amperage despite being connected to power indicating element failure or circuit problem.

“My generator starts fine without the heater—is it really necessary?”

Yes. While the generator may start without the heater, cold starts cause significant internal wear. Cold thick oil cannot flow quickly enough to lubricate bearings during the critical first seconds of operation causing metal-to-metal contact. Cold metal components have tighter clearances increasing friction during cranking. This stress damages bearings cylinder walls and piston rings. Over time repeated cold starts can reduce engine life by years. In cold climates a failed heater can prevent starting entirely when the facility most needs backup power. The heater costs pennies per day in electricity but prevents thousands in premature engine wear and potential no-start failures during critical outages.

How much does it cost to run a block heater continuously?

Block heaters typically draw 400 to 1500 watts depending on engine size. At average electricity rates this costs approximately 10 to 40 dollars per month to operate continuously. This minimal expense prevents cold start wear that can reduce engine life by thousands of hours and ensures reliable starting during power outages. The cost of replacing a starter or repairing cold-start damage far exceeds annual heater operating costs.

What causes block heaters to fail?

Element burnout is most common. Heating elements have a finite lifespan and eventually fail from thermal cycling. Mineral deposits from coolant can coat elements causing overheating and burnout. Corrosion of element housing allows coolant to contact electrical components causing shorts. Loose or corroded electrical connections create high resistance that overheats wiring. Voltage surges from lightning or utility switching can damage heating elements. Most failures occur gradually with heater losing heating capacity before complete failure.

Can I install a larger capacity heater for faster warmup?

Not recommended. Heaters are sized by the engine manufacturer to provide appropriate heating capacity without creating hot spots that could damage engine components. Oversized heaters can cause localized overheating or boiling in coolant system creating air pockets that prevent proper coolant circulation. Oversized heaters also draw excessive current potentially overloading circuits. If existing heater seems inadequate verify it is functioning properly before considering replacement with different capacity.

Should I turn off the heater during summer months?

Generally no. Block and jacket water heaters provide minimal benefit during hot weather but keeping them energized maintains their readiness and prevents moisture corrosion during periods of inactivity. The additional electricity cost is minimal. However in climates where utility power costs are extremely high and summer temperatures remain consistently warm, some operators choose to disable heaters seasonally. If disabled heaters must be re-enabled well before cold weather returns and tested to verify proper operation.