I had a new alternator put in my son's 2003 GMC Envoy, and immediately after the climate display graphics aren't working. The dealership said it was a bad circuit board now. Could it be something to do with putting the new alternator in?
Please check the supplied voltage over the battery terminals when the car is running. Also have someone inside the car to measure with increased engine RPM. The voltage should never go past 15 volts.
If it does, the voltage regulator might be bad or missing entirely as it often is integrated in the alternator. This could be an issue when an alternator of the wrong type is installed. If the supplied voltage is normal, then it likely is just a coincidence.