Yanmar 4LHA-HTP Operation Manual page 668

Chapter 9 Electrical System
7. Tachometer
Check if the sender is loosely fitted.
Measure the internal resistance of the sender.
(Tobe1.6±0.1kQat20 Q
o
Measure the output voltage of the sender.
(To be IV or higher at 20 Q
o
9-42
i No
4LHA Series
Yes Fix the sender securely.
No Replace the sender.
No Replace the sender.