How do you verify a supplier for Air Conditioners & Refrigeration Appliances power module?

Please verify the following points and require itemized written supplier responses:（Air Conditioners & Refrigeration Appliances power module） Define capacity, accuracy, materials and operating environment before requesting quotes on a uniform basis. Request specification sheets, test reports, certificates, maintenance manuals and spare-part lists. During acceptance, verify appearance, dimensions, functions, safety protection and packaging, and keep test records. Do not compare unit price alone; include customization, freight, spare parts, after-sales support and downtime risk. Keep written records of inquiries, confirmations, FAT, acceptance and warranty commitments.