Cadillac: 1996 sts trouble starting, battery voltage, heater core

Question
When I turn the key it hesitates before it turns over. Sometimes it keeps on cranking.The heater core was replaced and now the fan does not come on so I have no heat.Thanks so much for taking the time.

Answer
Could be a fault in the starter. Check for battery voltage on the "S" terminal of the starter post as you turn the ignition key ON. If you have battery voltage instantly at the "S" terminal every time, Have the starter tested.

Could be a fault at the:

blower motor electrical connections.
Ac/Heater programmer electrical connectors under the dash on the passengers side

Check all the connections where the work was performed.