my van stalls at different intervals and the steering wheel gets locked(Maybe the steering wheel doesn't move because the engine has gone off, never noticed that.) need help. Could it be the power steering fluid. please reply.

 

Next time when it stalls see if you can turn the wheel. even with the engine stalled you should be able to turn it very forceibly. if it doesnt turn and locks like the steering lock when the ignition is off i would look into something with the ignition key/switch mechanism. and the powersteering fluid would have nothing to do with this.