What are common defects of low-quality thermostats?

Common defects include drift, inaccurate differential, capillary leakage, loose contacts, poor heat resistance and short service life. Request samples and specifications rather than buying only by lowest price. Checklist: 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.