The MTA barely helps straphangers navigate around constant weekend service diversions — and in many cases fails to tell riders about line outages until after they’ve paid, according to a new report.

Over a third of subway- station entrance areas had no signs telling passengers about annoying outages, a survey by the New York City Transit Riders Council found.

“You should know at the very least before you pay,” said Andrew Albert, the council’s chairman.

“You shouldn’t go down a set of stairs and possibly onto a platform before finding out if your train is running.”

In a statement, the MTA said it’s adding 26 electronic display boards to stations to give customers real-time diversion information before they pay.