Why is my heavy-duty truck burning 20% more diesel fuel than last month?
A sudden 20% fuel economy drop usually means a clogged DPF, leaking injector, low tire pressure, or a stuck-open EGR valve —…
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Heavy-Duty Vehicles & Fleet
Practical, step-by-step fixes for heavy-duty vehicles & fleet problems — 62 published so far.
Why is my heavy-duty truck's alternator not charging the batteries properly?
A heavy-duty truck alternator stops charging when the voltage regulator fails, the serpentine belt slips, or battery cables are corroded, preventing the…
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Why is my heavy-duty truck's alternator not charging the batteries?
Your heavy-duty truck's alternator isn't charging because of worn brushes, a failed voltage regulator, loose or corroded battery cables, a broken drive…
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Why is my heavy-duty truck's DEF system throwing a fault code and derating the engine?
A DEF system fault with engine derate usually means the aftertreatment system detected a problem — like low DEF fluid, a bad…
See the fixWhy is my heavy-duty truck's DPF regenerating every 50 miles?
Your DPF regenerates every 50 miles because excessive soot accumulates too fast, usually from short trips, bad injectors, wrong oil, EGR issues,…
See the fixWhy is my heavy-duty truck's DPF regenerating too often?
Frequent DPF regeneration usually means the filter is clogged with soot from short trips, bad fuel, or a faulty sensor, preventing passive…
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Why won't a heavy-duty truck's batteries hold a charge overnight
Your heavy-duty truck's batteries likely won't hold a charge overnight because of parasitic draws from accessories, a failing alternator, sulfated batteries, or…
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Why won't my 2019 Kenworth T680's batteries hold a charge overnight in winter
Your Kenworth's batteries won't hold a charge overnight because cold weather cuts capacity by 50%, parasitic draws from ECM circuits drain them…
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Why won't my electric forklift battery hold a charge through a full shift?
An electric forklift battery that dies before shift end usually has sulfated cells, a failing cell, or a charger that isn't completing…
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Why won't my heavy-duty truck batteries hold a charge overnight?
Cold temperatures reduce battery capacity and increase internal resistance, so a weak or aging battery can't hold enough charge overnight. Parasitic draws…
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Why won't my heavy-duty truck's alternator charge the batteries?
A heavy-duty truck's alternator fails to charge when the belt slips, the voltage regulator malfunctions, or wiring corrodes, causing batteries to drain…
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Why won't my heavy-duty truck's batteries hold a charge overnight in cold weather
Cold weather thickens engine oil and slows chemical reactions inside lead-acid batteries, so a weak or aging battery can't deliver enough cranking…
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