Minnesota Attorney General Lori Swanson is suing a Texas auto warranty company for deceptive tactics, saying it's violating its promise of a full refund within 30 days.

The lawsuit is part of a broader investigation into extended auto warranty practices, Swanson said.

The state is seeking unspecified civil penalties and restitution for affected customers of Enterprise Financial Group Inc. of Irving, Texas. The company has sold more than 3,700 extended auto warranties to Minnesota customers since 2009, according to the state's lawsuit filed Wednesday in Hennepin County District Court. The warranties, also called service contracts, typically cost between $1,600 and $2,600.

Auto warranty companies have been a perennial source of trouble for consumers, from annoying robocalls and deceptive warranties to companies collapsing and leaving policyholders on the hook. In an interview, Swanson said she thinks the improving economy is creating an opening for bad sales practices. "These companies really seem to be on the uptick here," she said.

A bulletin her office issued Wednesday cautions Minnesotans about high pressure sales tactics and urges them to vet companies and contracts before signing up. Scout for prevalent loopholes, it says.

The warranty pitches are familiar to many Minnesotans. They come by official-looking postcards or phone calls: the warranty on your vehicle is running out, buy a new extended warranty from us. People may think they are getting bumper-to-bumper coverage when they are not.

Enterprise Financial Group did not return several messages seeking comment. Its website says it provides consumer and vehicle protection programs for dealers, financial institutions, insurance companies and manufacturers.

According to the lawsuit, Enterprise uses other marketing companies for sales such as Precise Auto Protection Inc. and Auto Processing Center.

The warranties go by a range of names such as TechChoice New Ultimate Coverage and Dent Zone Auto Body Guard PDR Contract and Vurge Full Throttle Coverage. They are different from the warranties that come with a new car, which are backed by manufacturers such as Toyota or Ford and typically cover a much broader range of problems.

Enterprise tells people they can cancel the contracts within 30 days of purchase for a full refund if no claims have been paid. However, the company makes it difficult for people to cancel with confusing instructions and runaround, the lawsuit said. Refunds are late or never come, and sometimes don't include the extra penalty payment the state requires if a refund takes more than 45 days. In one case, an elderly Minnesota woman trying to get her refund was transferred to about a dozen people on the telephone, some of whom hung up on her.

Another customer, Veronica Harper, a retired educational assistant in Eagan, said her refund took nearly a year.

"I think I kind of fell for it because my car was just hitting 100,000 miles," she said.

Harper said she paid $195 up front to get the policy. But when it came and her husband and son read it, they thought it was "bad," she said. So she canceled and tried to get her refund.

That took regular weekly calls, she said. She rarely got through to a live person. When she did there was resistance.

"One of the things they said is that, 'This isn't our department.' "

Swanson said the coverage provided by some of Enterprise Financial Group's contracts is woefully limited. Customers have to do car maintenance and oil changes according to a prescribed schedule and keep receipts, she said, or there may be no coverage for problems. One policy, she noted, stated that it does not cover "a gradual loss of performance which has resulted from normal operation and use."

Consumer advocates have for years urged caution over extended warranty plans in general. Consumer Reports has this to say on the subject: "You might be tempted to buy a service plan — also known as extended warranty — on your next laptop, dishwasher, or a new or used car. But chances are that what you spend will be money down the drain."