4000 Models
- Check battery and voltage stabilizer for proper voltage. Remove instrument cluster. Leave sending unit installed and connect Tester (VW 1301) between gauge and ground. Start engine.
- With dial set to 430, gauge should be within engine cold and warm-up range. With dial set to 60, gauge should be in overheating range. Keep tester connected for a minimum of 1 minute to allow gauge needle to reach checking points.