Thermostat first...cheapest fix.

Next. Aux fans. Normally running when the A/C is on and/or ambient temps are high. There should be a temp sensor of some sort that signals the fans to start up when temps get high...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car