I assume, if you have a flashing Fahrenheit display (light) you have auto climate control? If so, the flashing light indicates you have a fault in the system. The most common thing to cause a fault, would be low refrigerant level. Another problem is, the controller will loose memory of current settings if the battery is disconnected during mechanical service, without first turning the climate control OFF. Without voltage, the system controller will loose it's memory & calibration settings. Once the power is restored, the control unit will start in default (home) mode, searching & trying to recalibrate. It could take up to 50 ignition cycles to recover normal operation.