2005 MINI Cooper S electrical issue

Can a faulty key cause electrical problems with a car?
I have a 2005 Mini Cooper S with 132,000 Miles. I have two identical keys that can open the car doors and windows remotely. I use Key A almost exclusively. Occasionally I use Key B to make sure it is still usable.

After a recent deluge, some of the electronics and lights were not working properly. The car would start and run but the radio would not produce sound, the windows would not close all the way, the directional signals did not display on the instrument panel and the rear brake lights would illuminate after exiting the car but not while in the car if the light switch was not on.

I opened the hatch and noticed water on the trunk carpet and when I picked that up I saw that the battery well was flooded. I sponged out the water in the battery well but all the problems continued. To get the brake lights to go off I had to disconnect the battery.

I bought a new battery and at first start everything seemed to work fine while using Key A. But then the same problems came back. After numerous connecting and disconnecting the battery. I started the car with Key B. Everything started working again slowly, perhaps over two hours.

However, the next time I used Key A again, all the problems returned. So after connecting and disconnecting the battery everything started working again, slowly, perhaps over two hours but only using Key B. I’ve done the Key initialization routine on both keys. But I’m hesitant to use Key A again.

The key fobs shouldn’t cause the kinds of trouble you are having. It seems to me you may have at least some grounding issues and possibly power delivery issue. Make sure all the fuses are good and have voltage to them for the radio issue. Try cleaning the main battery and chassis grounds to see if that helps, especially in the areas where things got wet.