The National Highway Traffic Safety Administration said Friday it has opened probes into four new cases of alleged automobile safety defects and upgraded investigations in three other cases.

The government agency said in its latest report that it is investigating owner complaints concerning windshield wiper motor failure in 1986- through 1988-model Ford Aerostar minivans.NHTSA also opened an investigation into 1988-model Ford F350 trucks with 351 cubic-inch V8 engines for power loss; 1987 and 1988 Toyota Camry cars for defective front seat belts; and 1984 through 1988 Chrysler Laser and Dodge Daytona cars for horn failure.