Cadillac's Wild Voltage Swings Signal Alternator Trouble

I had a very similar issue with my 2003 Cadillac CTS and can share my experience as someone with moderate car repair knowledge. The symptoms matched yours exactly, erratic voltage readings, multiple system failures, and weird electrical behavior even after installing a new car battery. The voltage regulator ended up being the primary culprit, but it was actually part of a failing alternator unit. Here is what my repair process looked like: 1. Initially thought it was just a circuit protection issue 2. Had alternator tested, showed inconsistent voltage output 3. Workshop diagnosed a failing voltage regulator inside the alternator 4. Complete alternator replacement was needed as the regulator was integrated The electrical issue was causing the alternator to deliver inconsistent power, which explained both the low and high voltage symptoms. After replacement, all systems returned to normal operation. Total repair cost was 290€ including parts and labor. Before suggesting specific solutions, could you share: Any warning lights on the dashboard? Does the battery light flicker while driving? Have you noticed dimming headlights? Did you measure the actual voltage across the battery? This information would help confirm if your issue matches what I experienced.

Last service was at 181000 KM, just a couple months ago. Getting a second opinion next week since the original diagnosis suggests both a failing voltage regulator and potential car ECU damage from the power surges. The alternator failure seems most likely given the symptoms. My voltage readings swing between 11.2V and 16.1V while running. Definitely concerning since these fluctuations could damage other electrical components. Already have three repair quotes ranging from 350€ to 520€ for parts and labor, just trying to confirm the diagnosis before proceeding with the alternator replacement.

Based on your voltage readings, this is definitely matching what I experienced with my Cadillac. Those voltage swings between 11.2V and 16.1V are almost identical to what my car showed before the repair. The overvoltage spikes above 15V are particularly concerning as they can indeed damage sensitive electronic components. When my alternator was failing, the erratic voltage regulation caused similar circuit protection issues across multiple systems. I would strongly recommend getting the alternator replaced soon. In my case, waiting too long led to additional electrical issues with other components. The repair quotes you received are in a reasonable range, I paid 290€ but prices have increased since then. The power surge problem will likely get worse over time. While getting a second opinion is smart, the symptoms and voltage readings align perfectly with a failing voltage regulator in the alternator unit. A quick test you can do: measure battery voltage at idle, then at 2000 RPM. If the voltage difference is more than 0.5V, it further confirms the alternator regulation problem. This matches the test results I saw before my repair. Would suggest going with a repair shop that includes a solid warranty on the new alternator unit, as this will protect you if any related electrical issues surface later.

Thanks for confirming the voltage readings match your experience. Those are definitely concerning swings that point to serious high voltage regulation issues. Given my readings and your previous case, I am now convinced this is an alternator failure causing power surge problems. The diagnosis of both a bad voltage regulator and potential ECU damage makes sense, though I hope catching it now prevents further electrical system damage. My test readings of 11.2V to 16.1V while running seem to mirror your situation before the alternator replacement fixed things. Will proceed with the middle quote of 420€ since they offer a 2-year warranty on parts and labor. That seems reasonable given current repair costs. Getting the circuit protection checked as well to ensure no other components were affected by the voltage spikes. Really appreciate you sharing your experience, it helped confirm my suspicions about the alternator being the root cause. Will update once the repair is complete next week. Just hoping to minimize any additional electrical damage in the meantime.