2004 ZTS electrical problems

We just bought a used 2004 ZTS. My wife drove it three times and have had the following problems:
After applying the brakes to stop, the radio died and the dashboard lit
up with all lights. The car stalled for a second and then started back up. It has happened three times to her on the same trip.
It also stalled while sitting at stop light, the light turned green she put her foot on the gas and it died. It did restart after a couple tries with the key.
Another time she was starting it and it ran for a few seconds and then it died, she could not restart it and she took the key out of the ignition, got out of the car and the radio came on for some odd reason. She got back into the car and put the key back in the ignition and it started right up.
She took it to the dealer (under warranty) and they could not find anything. They kept it for a week and put a hundred miles on it (we told them to test it thoroughly). Any ideas?
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I can think of three possible causes for problems like that: a) it's been soaked. Did they check for water under the carpet, behind the dashboard etc. Do you have lakes or bridges over rivers nearby? Has it been wet in your area recently? b) the battery has an intermittent short. This can cause periodic quits, but I doubt that's your problem because it doesn't explain the dashboard lights etc. c) perhaps someone's been frigging with the wiring, maybe trying to install a remote starter or custom sound system. Did they pull the steering column cover and dash to check for damage? Cheap custom shops can sometimes do really stupid things to car wiring.
You don't say if the problems persisted after you got it back from the dealer. If they've gone away, or seem less, then number 1 is most likely. You might want to leave it in the sun as much as possible, with a window slightly open.
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Bad grounds can cause no end of weirdness, but are more common on older cars with corrosion. Fuel pumps can go, especially if you've run out of gas (they overheat if run dry) but I don't think could cause the other issues.
I think you've probably found the reason why the previous owner sold the car. These things can occur on any make and model (I haven't seen such complaints on the Focus very often) but they can be a pain to find and fix. If it was me, I'd start by buying a Focus wiring diagram, which I think can be bought from Ford through a dealer.
Upside is the problem, if you can find it, should be easy to fix and then you've probably got yourself a good set of wheels. Good luck.
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