Engine overheat indicator doesn't work as expected

The Engine heat indicator is defective and will never indicate if the engine is overheating. In our case, we had an issue where the water from the radiator tank was completely drained and we used it for about 10KM and the engine overheat indicator didn't indicate. There were all sorts of overheat issues later on - which meant that the car was in the Uppal service centre for about 2 months (don't remember exact times now) and had to cough up about 30k. The worst thing is that: the company never accepted that the overheat indicator was defective. Can't believe this company for any product further purchases for sure.