The Blackhawks turn it on, the way they always do

That on-off switch, the one the Blackhawks have been known to flip at the most crucial times?

On. Most definitely on.

The Team That Won’t Die wouldn’t again Saturday night, even when its vital signs insisted it was a goner. The Hawks beat the Blues 6-3 in a playoff game that went from darkness to light with a flick of a finger.

How the Hawks are able to do that has been discussed ad nauseam during their stretch of three Stanley Cup titles in six seasons. Look, it’s like this: They have great players who dig deep when things are tough, and their opponents seem to say “uh-oh’’ when the Hawks start rolling.

Not a scientific answer, but there you are.

Game 7 of this first-round series is Monday night in St. Louis, featuring a Blues team that should be shifting from doubt to a crisis of confidence right about now. They had a 3-1 series lead way back on Thursday morning.

On Saturday, after falling behind 3-1 in a brutal first period, the Hawks scored five straight goals.

They were dead, and then they weren’t. Just like all those other times. They are 13-4 when facing elimination in Joel Quenneville’s tenure as coach.

“It comes from these guys who have been doing it for a number of years here,’’ the Hawks’ Andrew Desjardins said. “They pass it on to new guys and guys who have been here for a few years. It’s just like a domino effect with that kind of mentality, that confidence, that whatever-you-want-to-call-it.’’

Down 3-1, the Hawks needed some help, a jumpstart, a couple of paddles worth of defibrillation. It came in the form of a hooking penalty on the Blues’ Kyle Brodziak three minutes into the second period. A power-play goal by Artem Anisimov at least gave the Hawks the impression they had an actual offense.

When Trevor Van Riemsdyk scored a goal to tie the game 3-3 later in the period, the United Center went into full bedlam mode. Decibel levels refused to drop to safe levels.

“My ears were buzzing,’’ Hawks forward Andrew Shaw said. “It was a special moment. We tied it up, and the crowd loved it, and you’ve got to feed off that.’’

Make no mistake: The Blues are very, very good. But if they didn’t understand what they were up against before that moment, they certainly did then. The floodgates were officially open. The Hawks outshot the Blues 19-6 in the second period. When their goalie, Brian Elliott, has nightmares, they look like that.

Less than two minutes after Van Riemsdyk’s goal, Dale Wiese one-timed an Artemi Panarin pass to give the Hawks a 4-3 lead.

That switch? Very much flipped.

When the Blues applied intense pressure in the third period, Hawks goalie Corey Crawford did a fair imitation of a brick wall. The goal that finally gave the Hawks some breathing room came on a power play in which they seemed more focused on burning the clock than shooting the puck. Patrick Kane found Shaw from behind the net, and Shaw slammed it home for a 5-3 lead.

Game. Series?

“I know we have momentum,’’ said Quenneville, who surely wants to see a better start Monday.

The game looked over halfway through the first period. The Hawks were terribly out of sync. Passes not in the right spot, the puck agonizingly out of reach.

When Desjardins missed an open net about 6:30 into the period, it was a killer twice over. He took a pass from Weise just outside the goalmouth and missed by the hockey equivalent of a mile. The Blues took the puck the other way, and Scottie Upshall scored seconds later. What should have been a 2-0 Blackhawks lead instead was a 1-1 tie.

The Blues would score two more times in the period, giving them three in a 4:42 span. There were many more opportunities, too, thanks to a Hawks defense that always seemed to be playing catch-up with the puck. Crawford was not great when he needed to be, but the people in front let him down. Blues players were allowed to camp out at the net. You would have been forgiven for thinking they were waiting for the release of the latest iPhone.

The Hawks looked tired, and maybe they were. But tired is for the offseason. The Hawks don’t do early offseasons.

So how did they get here, from that hideous first period to a 6-3 victory?

“It’s easy when you have a bunch of guys who have been through this before,’’ Hawks forward Andrew Ladd said.