I want to find out who my baby's father is without a dna test. can i use the old fashioned blood type testing?

Too vague: Blood type testing can certainly exclude a designated person if their blood type is incompatible with that of the child. For example, a dad who is ab would not have a kid that was an o. But narrowing down & proving someone is by this means is unlikely.There are some companies that offer dna tests for this purpose & some states will require this method to identify dads for child support disputes.

See below: Not reliably. It will positively rule our certain people, but not be as specific as you need.