Battery changed.......but

Hi all
I had to change my battery this morning as the old one had died. OK, so drove it just now and when I touch the break pedal the rear window heater light comes on in the dash, take foot off brake and light goes out. This never happened before so it's obviously something I have done while changing the battery. has anyone come across this before?
Cheers

What model?

Yeah that might help, 90 2.5 Td5 w plate

Seems bonkers and a strange coincidence to me. I'd be looking to see if there is anything causing a short in the wire harness that comes up in the tub behind the offside quarter panel. Behind the triangular corner panel. A lot of water in after all of this rain perhaps? There are a lot of terminals/connections there. (I'm presuming the rear harness comes in at the same point on your W plate as on my P plate.
Having said that, I'm no auto-sparky by any stretch. Just where I would start looking.

Sounds like you found the short that flattened the old battery.

Make sure you have removed the surface charge on the battery. Sounds like ingress water to me that Unless any one has messed with your electrics in the past it won't be a short. unscrew instrument warning light panel inspect wiring and terminals look for any corroded terminals or anything unusual also work all your other electrical instruments lights, wipers, horn, hazards etc. Could tell you a lot my 90 seems to get very damp in the winter