I have had three things fail on my 2003 A4 B6 in the last few weeks. First the alarm sender was sounding randomly and constantly at random times (most commonly diagnosed as the internal batteries on the sounder failing), the brake lights turning on randomly draining the battery (most commonly diagnosed as a brake light switch failure) and the engine coolant temperature sensor causing the gauge to fail and an engine light to come on (code P0118 on my OBD II) (most commonly diagnosed as sensor failure).

I removed the sensor from the bracket in the trunk and laid it in the trunk for access the next time it went off. It hasn't gone off since!

I changed the brake light switch but cant say that has solved the issue yet. What has happened however is that "it appears" that the ECT has started to function again. Can the brake light switch have an impact on the ECT sensor? I hope it can because I really don't want to change the sensor. I have read it is a dog to change!

Any wisdom appreciated.

Thanks,