PREVOST H3-45 2023 Operator's Manual page 254

B-8 Multiplex Troubleshooting
Problem / Symptom
Fire alarm pop- upand
audible alarm always ON
and there is no fire or
high temperature in the
engine compartment
The vehicle is parked and
the electrical horn is
activated to indicate a fire
in the engine
compartment but there is
no fire
A single light, a group of
LED lights or another
function of the vehicle is
not functioning
No backlighting in the
instrument cluster
The radiator/CAC electric
fans do not function and
the engine is overheating
Probable Causes
Short-circuited fire sensor or
defective sensor
Short-circuited fire sensor or
defective sensor
The multiplex outputs are
protected in current by an
internal "soft fuse". When an
output is shorted, it turns
OFF and stays OFF until the
"soft fuse" is reset
Circuit breaker CB10
tripped or fuse F10/F29
blown
PA-1652 Operator's Manual H3-45 Coach
Prior to start the vehicle, cycle the ignition
key to the ON position, OFF position and
then ON position again and then start the
vehicle. This will deactivate the fire alarm
function. This has to be repeated each time
the vehicle is restarted.
Cycle the ignition key between the ON and
OFF position twice within 3 seconds. This
will deactivate the fire alarm function. This
has to be repeated each time the vehicle is
parked
turn the ignition key to the OFF position and
turn to the ON position again. This resets all
"soft fuses"
is Check circuit breaker CB2, CB10
Check / replace fuse F10, F29
Check / replace relay R22, R23
You can manually engage the radiator/CAC
fans half-speed (50%) or full speed (100%).
1. On the Driver Information Display, select
DIAGNOSTICS
TESTS submenu
RADIATOR FAN SPEED 50% or FORCE
RADIATOR FAN SPEED 100%.
2. The DID status line will show TEST to confirm
the forced activation of the radiator fans. To
cancel, turn the ignition switch to the OFF
position or press ESCAPE button, select
TERMINATE TESTS & FORCED STATES
submenu and then press ENTER button
twice. TEST will disappear from the DID
status line.
Actions
menu. Select VEHICLE
and then FORCE