Does the ford focus voltage regulator have problems?

The Ford Focus's voltage regular is not prone to any Model Specific issues, and they don't fail at a greater rate than You'd see in any other vehicle. Still, that doesn't mean that Your results will always be consistent with this; in any case, Your voltage regulator may fail in one of several ways. In the Focus's case, the regulator is built directly into the alternator, so many voltage regulator problems can manifest as alternator problems. Unfortunately, there's no way to isolate it; if You're having serious issues, You'll need to replace the entire alternator. This can get quite expensive through moSTShops, but buying at a junkyard or through somewhere like eBay or replacing Yourself can mitigate much of the cost.