SN65HVD256: SN65HVD256 was found very high failure in commercial air conditioner PCBA from after sale.

Hi Mike,

Since the CANH/CANL pins would typically route to a connector, the most common cause of field failures tends to be over-stress induced on these lines.  This could be either a DC overstress (like an accidental short-circuit to a power rail) or transient in nature (such as an electrostatic discharge).  Protection components like TVS diodes can be used to help clamp transient overvoltages.  In this case, though, you should make sure the TVS is suitable based on the specifications of the transceiver.  You can read more about that in this blog:

For longer-term/DC stresses the best solution is usually to choose a transceiver capable of tolerating high voltages.  An example is TCAN1051HV, which is p2p with SN65HVD256 but is rated to support +/- 70 V on the CANH/CANL signal pins.

Regards,
Max