New Holland T8010 Manual page 1558

Engine RPM from the alternator is measured too high
Cause:
If the transmission controller detected the engine speed exceeds 3000 RPM, this fault code will be recorded.
Possible failure modes:
1. Tractor was in over-speed condition, such as run down hill with load.
2. Faulty signal.
Solution:
The engine speed signal is from the W terminal of the alternator. The RPM is displayed on the ICU.
This fault code is most likely being recorded when tractor was in over-speed condition, such as runs down hill with
heavy load. In such case, fault code 80 may be recorded too.
If it is sure the tractor has not been in over-speed condition or the fault code is active in normal conditions, go to the
following steps.
1. Make sure the alternator is the specified model and its engine RPM signal matches the specified model.
Make sure the belt and pulley are properly installed.
2. Troubleshooting by viewing the Instrumentation display
The engine speed is displayed when tractor is running.
Drive the tractor at different engine throttle and watch the speed.
If the speed display is normal, the speed signal is fine. The problem is more likely in the wiring connection from the
alternator to the transmission controller. Go to step 4.
If the engine speed display is higher than it should be, go to next steps.
3. Disconnect the wire connection at the W terminal of the alternator. Clear all trans faults. Run the tractor and
check trans faults again.
If fault code 79 appears again, There is good chance the higher than normal signal is coming from other signal
sources. Go to step 4.
Otherwise, check the signal at W terminal of the alternator.
4. Check the wiring from the alternator to the transmission controller.
Check from W terminal of the alternator to pin 33 of connector 351.
Pay attention to connection crossing among wheel speed sensor circuit, engine RPM signal circuit, and PTO speed
signal circuit.
Looking for wiring shortage, loose connectors, and bent pins.
5. Check the signal at W terminal of the alternator.
The signal is in half-wave rectified sinusoidal output (close to square wave) form.
The signal will show around 7 V DC (will increase as engine speed goes up) and 0 to 14 V AC.
At 1000 engine RPM, the AC signal will have around 290 Hz Frequency.
At 2000 engine RPM, the AC signal will have around 580 Hz Frequency.
If the engine speed signal is normal, check connections from the alternator to the controller.
If the engine speed signal is not normal, replace the alternator.
Section 55 - Electrical System, Controller - Chapter 4
FAULT CODE TRANS 79
55-4-31