The Rail, Tram and Bus Union revealed its plan last month but it was withdrawn after a legal threat from the government. It was revived with a ballot for members to take protected industrial action.
Members voted overwhelmingly in favour of the action, the union said.
"This has sent a very strong message to the NSW government that RTBU members are prepared to fight for their right to take action and the (enterprise agreement) they deserve despite the vile threats from a desperate government," RTBU NSW secretary Alex Claassens said in a message to members on Wednesday.
The government is yet to be informed when the union will disable the Opal readers.
Transport Minister David Elliott said the union's plan was unsafe and ridiculous, calling it economic vandalism.
"Step away from this ill thought out strategy and focus on providing commuters with the reliable services that they deserve," Mr Elliott said on Thursday.
"Should the action go ahead I'll take whatever action is necessary to protect commuters."
Mr Claassens warned members the government may apply for an injunction in the federal court, despite the protected action ballot.
"We do not know if it is a real threat yet, but we need to be ready for the possibility," Mr Claassens said.
The rail union took industrial action throughout August, which involved leaving Opal gates open, among other measures including area-based strikes and refusals to drive foreign-built trains.
Premier Dominic Perrottet said the union was moving to deactivate the readers because most commuters were still paying for their trips when station gates were left open.
Multiple unions have been seeking a new enterprise agreement for rail workers, while the RTBU is also pursuing modifications to a fleet of Korean-built intercity trains it argues are not yet safe to service NSW.Â
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