Some things you take for granted. Flip a switch and lights flash on. Turn the faucet knob and water flows. Cruise through the tollbooth and your E-ZPass records the right amount.

Except when it doesn’t. That was an unpleasant surprise for John McNally.

The Quakertown software trainer last month consulted his E-ZPass statement to look for tolls he had paid while on the job, so he could be reimbursed.

He was surprised to find a number of $10 charges that should not have been there — 10 in February and four in January.

When he mentioned this at his office, the first two coworkers he talked to checked their accounts and said they found similar unexplained charges.

“They seem to come up when it doesn’t read your transponder,” McNally says. “Instead of $2.80, which I usually pay, they were charging me $10.”

Curious, McNally, 58, looked through his 2018 statements and found more unexplained charges, but in $5 amounts.

“It seems like in 2019 they doubled the penalty for their equipment not working,” McNally says with a laugh. He was right, in a way. The charge for a missed toll did double when turnpike tolls were raised at the start of the year.

E-ZPass technology is pretty remarkable. For customers, tolls are automatically paid when they drive through a tollbooth. For noncustomers, pictures are taken of the license plate and bills are mailed. But no technology is perfect.

While I was waiting for a callback from the E-ZPass people, I skipped around the internet.

Consumer Affairs, the website of Consumers Unified LLC, had myriad complaints about E-ZPass from New York to Hawaii. Most had to do with wrongful violations and billing errors.

A Pittsburgh TV station did a report on motorists who had been wrongly billed.

A New York TV station reported on E-ZPass readers that were not recognizing the credit cards on file.

In New Jersey, a married couple were being charged as if their cars were trucks with three axles.

When McNally called E-ZPass, “the people I spoke to were great, they were very pleasant,” he says. In short order, $312 had been placed in his account, wiping out the erroneous charges.

“I’m just wondering how many people are out there who don’t have a clue” they have been overcharged, says McNally.

There might be many, because Pennsylvania E-ZPass has 3.2 million customers, says Laura Quick, manager of electronic toll collection customer service operation. Over the years, she says, E-ZPass has found that 1 or 2 percent of customers have complaints. That’s a low percentage, but 1 percent of 3.2 million is 32,000 people.

Quick wasn’t familiar with McNally’s case but says most problems come from misplaced transponders, the device that customers are supposed to attach to the windshield, behind the rearview mirror. “Typically [customers] say, ‘My transponder isn’t working,’ but when we take a look, lo and behold, it’s not mounted properly,” says Quick.

Some customers hold them in their hands, others lay them on the dashboard. Neither will work efficiently, she says.

“I always tell people they should routinely look at the charges, just as they would their credit card or bank statement,” Quick says.

If you find a mistake, call the E-ZPass people and they will fix it.

Their willingness to do so was a pleasant surprise for John McNally.