1. Check wires. Short 2 contacts on 053 919 501 A that shows temp on dashboard.
2. Put ignition key and switch on car (don't start). If temp gauge arrow moves to 90, switch off.
3. DO NO HOLD ignition making arrow reach max temp, because you risk damaging the gauge.
4. If temp is not stable - sometimes shows lower, sometime 100, change 053 919 501 A.
5. If new 053 919 501 A didn't help, check thermostat hose - warm means thermostat is open, fans switch on means that radiator switch works. Working temp is 90-95 is OK on ABT engine. Then check dashboard itself. Maybe problem is in gauge contacts or voltage regulator.
6. 053 919 501 A only shows temp and signals about overheating on dashboard.
7. 053 919 501 A DO NOT SWITCH ON the fans on radiator.
8. Fan switch is located at the bottom of radiator on thick thermostat line at engine bottom.
9. Car gets coolant, it reaches 85, thermostat opens, coolant moves to fan switch on radiator heating it to 95, fans cool down the engine to 90 or less and cycle repeats.
10. Cap on coolant tank should not be tight to release pressure.