MacDon FFT FD75 Assembly Instructions Manual page 204

1. Position header 150 mm (6 in.) above ground, and rest
it on safety props. Unlock adapter float.
NOTE:
If header is not on down stops during next two steps,
voltage may go out of range during operation causing a
malfunction of auto header height control (AHHC)
system.
2. The pointer (A) on float indicator box should point at 0.
If it does not, adjust cable take-up bracket (B) until
pointer (A) on float indicator box points to 0.
3. Use a voltmeter (A) to measure voltage between
ground and signal wires at AHHC sensor in float
indicator box.
NOTE:
The voltage reading should be below 4.3 V.
4. Fully lower combine feeder house, and float header up
off safety props (float indicator should be at 4, and
adapter should be fully separated from header).
NOTE:
You may need to hold HEADER DOWN switch for a few
seconds to ensure feeder house is fully lowered.
5. Use a voltmeter (A) to measure voltage between
ground and signal wires at AHHC sensor in float
indicator box. It should be at low voltage limit for
combine—0.7 V.
6. If sensor voltage is not within low and high limits, or if range between low and high limits is insufficient (on this
combine, it should be at least 3.0 V), make adjustments according to
214325
SETTING UP AUTO HEADER HEIGHT CONTROL
Figure 5.117: Float Indicator Box with Auto
Header Height Sensor
Figure 5.118: Checking Voltage with Voltmeter
Figure 5.119: Checking Voltage with Voltmeter
Adjusting Voltage Limits, page
194
197.
Revision A