Originally Posted by
seven ends
Any codes? Being old school, I would start by looking for an electrical problem first, like low voltage from a failing battery or generator. The A/C loads up Cabin fan motor and Radiator fan motors requiring system voltage and when you are at idle you are not getting optimum output from the Generator. Also would suggest to check grounds esp. any recently removed and replaced, the EBCM ground, HVAC/Fan grounds. EBCM could be defective worst case though without knowing anymore than your post above I am leaning towards insufficient voltage condition.