I have a 2004 V70, and just noticed this morning that both brake lights stay on regardless whether the car is running or not. The high brake light in the upper part of the rear door works properly. Any ideas what the problem might be?

Since the middle light works properly, this would would indicate that the brake light switch is working OK.

You problem kinda sounds like one of the relays in the Rear Electronic Module (REM) may be hanging closed. They are cheap little relays and there are a bunch of them for the various things like lights and door locks, etc. To make matters worse, as I recall, there are relays that feed other relays. So since it is BOTH lights that acting up you want to look for something that is common to both of them but do NOT involve the middle light.

This wiring diagram may help might:

http://www.matthewsvolvosite.com/downloads/2004_V70_XC70_V70R_XC90_wiring_diagram.pdf

Thanks very much for the suggestion and wiring diagram, Chris. I spent the last hour pulling the rear interior apart since the brake relay was hidden from the little trap door on the side. Of course after all that my lights work fine! Pulled the relays out and put them back in so I could feel like I accomplished something useful. At least I know how to get at them now.

Glad to hear it's working.

You weren't confusing brake lights with rear fog lights, were you? (Actually, I think most of the wagons only have fog on the LH side.)

I wasn't sure what was what at first, but then figured out which was the brake vs. fog lamp. Still works fine, for whatever reason.

Go in the back of the car where the relay is. have someone step on the brake. The relay you are interested will buzz. I believe it is blue at least on the 2003 it was.

my situation was slightly different where brake light didnt work after successful bulb changes.

the relay is a common issue.

Thanks. Excellent idea!