Buick Rainier's Electrical Gremlins Draining Battery Life

Had a similar situation with my 2007 Buick LaCrosse that turned out to be more than just a weak battery. The symptoms matched perfectly, multiple overvoltage codes, electrical system glitches, and difficult cold starts. The voltage regulator inside the alternator was failing, causing power surges throughout the electrical system. This alternator failure was damaging the battery by constantly overcharging it. The battery would get heavily discharged between drives because the electrical system was not maintaining proper voltage. The fix required replacing both the alternator and battery as a set. The old battery was permanently damaged from the repeated power surges. This was a serious repair since the faulty alternator could have potentially damaged other electronic components if left unchecked. Testing confirmed the alternator was outputting inconsistent voltage, sometimes too high, sometimes too low. This explains the unusual electrical issues you are experiencing. Would strongly suggest having both alternator and voltage regulator function tested, not just basic battery tests. These electrical issues typically worsen over time and can leave you stranded when the alternator finally fails completely.

Thanks for sharing your experience with the LaCrosse. I encountered nearly identical circuit protection warnings and electrical problems on my Rainier last winter. Got it fixed and running smoothly now but it indeed required both alternator and battery replacement when the voltage regulator failed. Did you remember roughly what the total repair cost was? Also curious if you had any related car electronics issues pop up afterward? Mine has been stable since the fix but always good to know what to watch out for.

Good to hear your Rainier is running properly now. For my LaCrosse, the total repair bill was much more reasonable, got the overvoltage problem resolved for 290 with a new battery. The mechanic found the battery was heavily discharged and starting to fail, but luckily caught it before any alternator damage occurred. After the battery replacement, all the circuit protection warnings and high voltage alerts cleared up completely. The electrical system has been stable for months now with no power surges or related issues. Regular voltage testing shows everything staying within normal range. This type of electrical issue can cascade into bigger problems if left unchecked, so catching it early likely prevented more extensive repairs. If your fix included both components, that was definitely the thorough approach to prevent any recurring electrical issues. For preventive maintenance, it helps to get voltage readings checked during routine service to catch any developing alternator failure or battery problems early.

Thanks everyone for the input. Finally took my Rainier to get checked out last week. The mechanic confirmed what was suspected, a failing voltage regulator in the alternator was causing power surges through the car ECU and other systems. The total repair came to 850 Euro including both a new alternator and car battery. They showed me how the old battery was severely degraded from the constant overcharging. The mechanic also ran a full electronic diagnostic to ensure no other components were damaged from the power fluctuations. Been driving it for a week now and all the electrical gremlins are gone. No more warning lights, all systems working normally, and the cold starts are much stronger. The shop suggested getting the charging system tested during future oil changes just to stay ahead of any potential issues. Really glad I got this fixed before the alternator failed completely and left me stranded somewhere. Definitely worth the repair cost for the peace of mind.