Iveco Stralis AT/AD. Manual — part 330
When fan action is not required for proper engine operation, the Front Frame Computer center pilots the compressed air electro
valve to move piston (8), displaces permanent magnets (3) from fan hub (2). The magnetic field generated by magnets (3) is
not enough to move fan hub (2) by induction.
The fan may rotate slowly due to friction present.
001676t
1
2
3
6
8
III.104
ELECTRONIC SYSTEMS
S
TRALIS
AT/AD
Base - January 2003
When low speed action is required, the Front Frame Computer center discharge air from duct (10) through the compressed
air electro valve; piston (8) moves and draws permanent magnets (3) towards fan hub (2). Piston travel is ensured by return
spring (7) and blades (4).
The shaft rotates at the same speed as pulley (1) and the effect of the magnetic field generated by magnets (3) is to make fan
hub (2) rotate at the maximum speed of 650 rpm.
For F2B the first speed is always connected since there are no pneumatic solenoid valve nor air exhaust system inside the
assembly.
001677t
2
3
10
1
2
3
4
6
7
8
ELECTRONIC SYSTEMS
III.105
S
TRALIS
AT/AD
Fan with low speed cut in (F3A)
001678t
When low speed is not enough to properly cool the engine, the Front Frame Computer center pilots second speed cut-in by
exciting coil (11).
The magnetic field generated by the coil attracts fan hub (2) floating ring (9) to pulley (1) making the two units solidal.
In this condition fan speed is the same as pulley speed.
1
2
9
11
III.106
ELECTRONIC SYSTEMS
S
TRALIS
AT/AD
Base - January 2003
001697t
Defect
The fan always rotates at low speed
Defect identification
Cause
-
Air supply pipe clogged
-
Air supply pipe broken
-
Center output does not pilot the coil
-
Interruption of the center to coil wire
-
Coils short-circuited
-
Improper mechanical parts sliding
The fan does not rotate above 650 rpm (low speed)
The fan always rotates at second speed
-
The center output always pilots the coil
-
Improper mechanical parts sliding
1. Engine brake switch - 2. Steering Wheel Interface - 3. Instrument Cluster - 4. Fan electro valve - 5. Front Frame
Computer - 6. Body Computer - 7. Fan electro valve - 8. Conditioner pressure switches - 9. Conditioner - 10. EDC -
11. Water temperature sensor - * The pressure switches involved in fan control are the (18-22 bar) conditioner coolant
pressure warning ones.
18 BAR / 22 BAR
MIN /
MAX
1
2
3
4
7
8
*
9
5
6
10
11
*
* Pressure gauges for engine fan control
ELECTRONIC SYSTEMS
III.107
S
TRALIS
AT/AD
Fan control diagram (F3A)
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