(MG Hector plus petrol automatic-1 year old). My car's battery was suddenly getting drained in just 2 days of not using the car. This happened twice. I took the car to the service centre and they said you have changed the horn which is not their brand's and its wattage is little bit more~1-2watts. And the wiring of the new horn is such that the relay of the horn is always in switched on position. Hence the battery is getting drained in 2 days. [But the horn was installed 6-7 months ago. Never faced the problem before, why now. And my car use frequency in these last 6-7months has been the same- using car few times a week] . The relay is always on but it does not activate the horn(no sound) unless horn is pressed from the steering wheel.

Okay so before finding the horn the reason for battery draining, they checked the battery with the battery health checking machine 3 times and all the 3 times the machine's result was to replace the battery. They then charged the battery for 1 hour saying as my car is not used a lot hence the battery's gravity has become low. After the charging finished, they checked for leakage in the car's system and did not check the battery again with that health machine. Then they said to install the original horn after which they can check the system again.

The car is only 1 year old and MG-Morris Garages gives only 1 year warranty on battery (Hyundai gives 3 years). As its only 1 year warranty, I feel the battery quality is not as good and if the car is used everyday, the battery problem could not be discovered for more than a year. But if car is used few times a week, like my case, it will be known sooner. This is just one thought. If I install a battery directly from the same battery manufacturer, they give 55 months warranty. (Battery installed is an exide 60AH maintenance free battery)

Can someone please clear my doubt. I want to know if the horn's relay is always in switched on position but horn is not activated (no sound) , will it still drain the battery? Thanks

  • 1
    Welcome to Motor Vehicle Maintenance & Repair! My understanding of most horn circuits is, the relay should power the horn directly. There's a separate circuit which powers the relay, and that circuit is what goes through the steering wheel button. Both always have power to them, but unless the circuit is completed, there's no power usage or drain. The horn is an "always available" circuit, I assume for safety reasons. The car shouldn't have to be running for the horn to work. I'm not directly familiar with the Hector, but would assume it is setup the same way. It is a very standard setup. Commented Mar 9, 2022 at 11:13
  • Did you wire up the new horn?
    – HandyHowie
    Commented Mar 9, 2022 at 15:49
  • Thanks for replying. @HandyHowie A car mechanic wired the horn Commented Mar 10, 2022 at 11:22


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