Took 24V out of a 12V PSU to power a peltier module, the psu died
The −12V rail on PC power supplies is not designed to sink large currents. It's usually limited to well under 1&nbsp;A, often even 200&nbsp;mA or less. Injecting a current of 5A or more from the +12V rail is likely to have damaged the −12V regulator.

As this appears to be a cheaply built PC power supply, the most expedient solution will be to replace the unit. Testing and replacing individual components will not be cost-effective, and may cause further damage.

Additionally, the TEC you are using is rated for a maximum voltage of 16.2&nbsp;V. Exposing it to 24V may have caused irreparable damage to the TEC as well.