Our client called with a case where their insured worked on the claimant’s vehicle, a 2005 Peterbilt 379.   The next day it caught on fire.   The client needed to know the origin and cause of the fire and if the work performed by the insured caused or contributed to the fire.   The vehicle was originally located in Arizona but was sold for salvage and moved to Washington state.   Our assignment was to inspect and photograph the claimant’s vehicle, research recalls, review client supplied documents, and identify the origin and cause of the fire.


After the fire the claimant sold the truck to an unrelated party for salvage and components were being removed as needed to repair other trucks in their fleet.   Other experts inspected the truck at least three times prior to our inspection.

We examined the exterior of the truck.  The truck’s car carrier rack, the fifth-wheel assembly, the second axle inner tires, and the third axle wheels and tires were missing.   The remains of the hood/front fender assembly were removed after the fire.

A common agreement of the other experts was that the fire had started in the left rear of the engine compartment.   The fire patterns confirmed this as the origin of the fire.


The fuel injection system was examined.   No indications of fuel wash or fuel spray patterns were found at or near the fuel injectors.   The fuel lines’ connectors were found in place and slightly heat damaged.   The rubber fuel hoses, routed through the left side of the engine compartment, were undamaged beneath the fire’s burn area.   No fire damage was found at or around the turbochargers, which were mounted on the right side of the engine.

The engine oil dipstick was removed for examination; the oil was found in good condition and at the proper level, and the oil filter was found in place and properly tightened.

We reviewed a National Highway Traffic and Safety Administration, Recall Campaign (Peterbilt Recall Number 1205E0).   This recall dealt with possible abrasion damage and a resulting oil leak from the Variable Valve Actuation Line rubbing against the sharp edge of the cylinder head, however this recall issue did not cause the fire.

The power steering system was examined, as was the air conditioning system.   The fluid lines and hoses were found intact and undamaged.   The fire pattern did not suggest a power steering system fire cause or an air conditioning system fire cause.

The radiator was not fire damaged, and the radiator header tank (mounted at the upper rear of the engine compartment) was insignificantly damaged. The coolant was examined and found at its proper level.   The water pump, located at the right front of the engine, was not involved in the fire.

The engine compartment electrical system was then examined.

The batteries were not damaged in their compartment at the lower left rear of the cab.   No localized heating was found at the battery compartment terminals or cables.   The battery ground cable was found in good condition.   We found slight fire damage to the battery cables and adjacent wiring harness above the starter.   The alternator, mounted at the upper right side of the engine, was not damaged and still freely turned. The alternator power supply cable sustained a heavy short-circuit that severed the cable as it contacted the braided steel-covered fuel return line after the fire had consumed the insulation on the alternator power supply cable.  The cut alternator cable again short-circuited against the “field” cable of the alternator.   These electrical activities occurred after the ignition of the fire and were not the cause of the fire.   Other small short-circuits were found on this cable, but none of the short-circuits on the alternator power cable caused or contributed to the fire.

The rubber plugs for the cables and wiring routed from the engine compartment fuse box were found damaged from their inside area.   Many of the power cables and wires connectors were found loose in the connector plug bodies, mostly due to old age and general wear and tear.   This resulted in high resistance electrical connections across the plugs.  The paint discoloration and heat patterns, found behind the protected areas of the plug bodies indicated that this was the point of origin of the fire, as a fire from within the engine compartment would not have burned this area.

The cause of the fire was the high heat produced by the loose connectors within the plug bodies.   The worn connections in the connector plug bodies caused high resistance electrical connections; which generated increasing heat.   The high heat melted the rubber and plastic insulation and plastic in the immediate area and ignited the fire.   The fire then spread outwards from this area.   The melted wiring harness insulation then allowed more short-circuits to form in the wiring harness.


The fire then entered the interior of the truck through the openings in the left side of the firewall and damaged the dash, steering column and wheel, upper front console, tops of the seats, and the upper area of the sleeper compartment in the interior.   Smoke and heat damage was found on the remaining interior components.

The day-before-the-fire service by the insured was not in the fire area.   The closest service area to the fire area was the replacement of the fuses for the cigarette lighters; the insured’s fuse replacement did not disturb or displace the fuse box or the subject wiring and did not cause or contribute to the fire.