Staff Answer
Sep 20, 2026 - 11:04 PM
If you've already replaced both the blower motor and resistor and the fan still won't come on, the most likely culprits now are the blower motor relay or the HVAC control module.
Start with the blower motor relay. It's located in the fuse/relay box under the hood. Swap it with an identical relay from the same box to test it quickly without buying anything. Also re-verify the blower motor fuse hasn't blown even after your repairs.
Next, check for proper voltage at the blower motor connector with a multimeter—if you're getting voltage at the connector but the motor won't spin, the new motor may be defective. If you're getting no voltage at all, the problem is upstream—pointing to the HVAC control module or wiring between the control module and the blower circuit.
On the 2016 Optima specifically, a faulty HVAC control module is a known issue and is often the missed culprit when blower problems persist after replacing the obvious parts. Have a shop run a bidirectional test on the blower circuit with a proper scanner.It'll confirm whether the control module is sending a signal or not, and save you from further guessing.
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