Zetor PRIMO HT 20 NC Operator's Manual page 45

(8) Engine oil pressure warning light It comes on if the engine oil pressure is insufficient
while driving.
NOTE
When the oil pressure warning light comes on, it indicates a malfunction in the lubrication system.

Immediately check the engine oil and, if necessary, have the vehicle repaired by the service center.
Water Temperature Warning Light
If this light comes on, the coolant is overheated.
NOTE
If the coolant warning light comes on, it is overheated, check it.

Engine Warning Light. If it comes on, there is an engine failure.
Notice: If the engine warning light is on, make sure that the operator drives the tractor only if
normal engine speed is reached. Failure to follow this instruction may result in reduced performance
and an accident caused by a system error.
(11) Cruise Control Indicator Light
This light is on when cruise control is on.
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TRACTOR CONTROLS