What electrical problems on your wife's car?
Common ones on Mustangs:
- Original battery goes bad at around 3 years, and the low voltage makes the electronics do wierd stuff.
- Smart junction box in the passenger footwell can get wet and cause problems. Check if the carpet is wet under the floor mat in that area. Also check that you don't have leaks or clogged drain at the cowl.
- Positive battery terminal connector under the rubber cover can get corroded.
- Ground connectors near the radiator can get loose.
- If you leave the CD changer on when you shut off the car, it sometimes can drain your battery.