Like most crossbreeds, the personality of a Chiweenie depends on the parents and how they have been bred and reared, but both the Chihuahua and the Dachshund are affectionate companion dogs who bond closely to their owners.
The personality of a Chiweenie seems to be more consistent when they are first crosses (F1). As if a line is successively bred, they can be either bred back to one of the original breeds (and so strengthen either the Dachshund or the Chihuahua personalities) or else be bred to another Chiweenie - in which case there is less predictability in temperament (and in-breeding becomes more of a potential issue).
Responsible breeders should be prioritising behaviour as highly as health and so it is important to find a good breeder. A well-bred Chiweenie should be outgoing and confident and not nervous, shy or fearful, and never aggressive.