When can a landlord enter a property

[Andrew Junquet]

Just took over being landlord of a single property I rent out. I've had the same tenant for 4+ years and had to let the PM go because he kept doing things like losing her rent check. I called her today to introduce my self. I asked if there were any current issues and she brought up that the light/fan in the living room doesn't work at all. My question is how do I go about entering the property to take a look at it? Can I just call and give her a 24 hour notice or does it need to be a written notice? 

Thanks!