Case IH 2235 (6157.06) - DEC – DEC:

Check alternator drive belt for slipping, cracking, or breakage

Measure alternator output voltage at the battery terminals (should be 13.8–14.4 V at idle)

Inspect wiring harness and connectors between alternator and battery for corrosion or damage

Test battery condition — a faulty battery can mask or trigger charging faults

Check the charge warning light circuit and voltage regulator