VISION
D R I V E R S H A N D B O O K
100
HesT indicator (High exhaust system Temperature).
An instrument panel indica-
tor which appears when the exhaust temperature is unusually high due to recent
regeneration. This is a normal behavior of the aftertreatment system, intended to
notify the driver and technician that the exhaust system temperature is high and that
caution should be observed around the exhaust system.
dPF indicator.
An instrument panel indicator which displays when particulate ac-
cumulation has reached a preset level in the DPF, and regeneration is needed. The
bus should either be operated with a more demanding duty cycle until the indicator
goes off, or it should be scheduled for a Stationary Regeneration at a service facility.
Levels of Notification
Regeneration—the process which clears soot accumulation in the DPF—occurs au-
tomatically as the bus is operated, as long as certain operating conditions (such as
minimum speed thresholds) are met. When bus operating conditions do not provide
adequate opportunity for the regeneration system to keep the DPF clear, soot be-
gins to accumulate. A system of driver alerts keeps the driver informed of when the
exhaust system is in need of regeneration, and of high exhaust temperature associ-
ated with regeneration. Several levels of regeneration alerts occur in sequence, each
indicating a more imperative warning.
High exhaust Temperature notification.
The High Exhaust System Temperature
(HEST) indicator appears to alert the driver when exhaust temperature is unusu-
ally high and that prudent judgement should be applied regarding the proximity of
people or combustibles to the exhaust system. For example, the bus should not be
parked on a surface of grass or weeds.
With the Cummins engine, the HEST indicator appears whenever the exhaust
temperature is high (752°F or above), regardless of moving speed.
The driver should be familiar with and abide by all instructions, warnings, and
cautions in the engine manufacturer’s operator’s manual regarding safe operation
when the HEST indicator is on.
• The HEST alert appears in the instrument panel.
• The audible alarm sounds one beep.
The HEST alert appears in the instrument
panel’s warning bank.
HEST Notification
The audible alert
sounds one beep.
Summary of Contents for VISION 2011
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