Defected truck and tachos

Hi guys and girls,

How long can a vehicle with a defective tacho be used before its breaking the rules?

The tacho itself is not defective but the information it’s being given by the truck is. The main computer is totally fried and showing not moving while driving, or vice versa (impossible to record a break) so the tacho itself is not defective but it’s not able to record accurately.

The truck has been back and forth to the dealer but they are unable to find the fault and fix it (problem is intermittent) but the boss is adamant I have to take it out tomorrow despite it being defected for the past 3 days in a row (last 2 by me)

I was under the impression a vehicle could only be used for 48hrs with a defective tacho but was told this by a DCPC trainer so thought it best to see if anyone here had the correct information before I go speaking to the boss about it.

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