Number of impulses
Driving speed
Constant
377
Model Code Page
34. Autocontrol ---III
15. 6. 1992
6600E, 8100E
342 7
F. Fault tracing, speed sensors (FREQUENCY INPUTS)
The following speed sensors are fitted on E---models:
--- R a d a r ( Radar)(A1C/7)
--- G e a r b o x s p e e d s e n s o r ( Gearbox) (A1C/30, 10)
--- Front axle speed sensor (Front axle) (A1C/29, 9)
--- Rear wheel rotation speed sensor (Rear wheel) (A1C/27, 8)
--- Engine rotation speed sensor (RPM engine) (A1C/31, 12)
--- PTO rotation speed sensor (RPM Pto) (A1C/28, 11)
N.B.! The speed sensor resistance (not radar) should be 1,0 ---1,10 kΩ which can be measured from connector X2C (pins, see
wiring diagrams) or from the lower ECS connector A1C (pins, see above). If the resistance value is infinite a new measurement
should be done from the sensor poles so that possible faults on wiring can be localised. A faulty sensor should be changed, see
page 341/1.
a) Checking radar
Drive the tractor at different speeds and write down impulses from the radar. The following values were measured from a radar
which was in a perfect condition:
D ~ 38 (1 km/h) (inaccuracy increases at low driving speeds)
D ~ 157 (4,3 km/h)
D ~ 327 (8,8 km/h)
D ~ 416 (11,4 km/h)
D ~ 757 (20,6 km/h)
D ~ 1026 (28,2 km/h)
--- If number of impulses from the radar correspond to values above, the radar is in perfect condition.
--- If no impulses come from the radar or if they deviate much from the values above, the radar is faulty or its wiring is damage.
b) Checking speed sensors for front axle, rear axle and gearbox
a) Drive the tractor on a road at a speed of 1---2 km/h and write down impulses from the radar (T1) and from one of the speed
sensors (A1).
b) Drive then with a faster speed (~ 20 km/h) and write down impulses from the radar (T2) and from the speed sensor (A2).
c) Equation A1/T1A2/T2 must come true (deviation can be
0,16).
--- If the equation comes true, the speed sensor is OK.
--- If the equation does not come true, the speed sensor in question, its adjustment, wiring or impulse disc is faulty.
c) Checking rotation speed sensors for engine and PTO
a) RPM engine; impulse value is about 0616 at engine revs 1000 r/min.
b) RPM Pto, impulse value is about 0364 at the PTO speed of 540 r/min.
--- If impulses from the sensor correspond to values above, the sensor is functioning properly.
--- If no impulses can be observe or number of impulses deviates much from values above, the sensor is faulty. Check then the
wiring and the sensor.
d) Calibrating and fitting speed sensors, see page 341/1.
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