New Holland TS90 1998 tachometer problem

[Roadworthy]

I don't have a wiring diagram but I do have a suggestion. You seem to have the problem localized to the cab - more specifically the instrument cluster within the cab. It seems to be thermal, related to expansion and contraction. Look very carefully at the connectors to your dash. Sometimes a wire will not be crimped correctly in a connector. I had the experience of the insulation being crimped into a connector but not the wire. Your issue may be hard to spot. By all means check grounds but look with suspicion at all points connected. These things do happen.

 

[JiiN]

All wires were nicely attached in connector. I't would help a lot if someone could tell me which color is the tacho's signal. And where there are connectors i should check than the connector in tacho?