Dying XTS Battery Drains Power From Multiple Systems

Had the same alternator issue on my 2012 Cadillac CTS last winter. The symptoms matched exactly, weak starts, dim lights, and low voltage readings across electrical systems. Initial testing showed the battery terminal connections were fine, but a proper voltage test revealed the alternator wasnt maintaining correct charging levels. The voltage regulator inside the alternator had failed, preventing proper battery charging during normal operation. The repair involved replacing the complete alternator assembly since the voltage regulator is integrated. During diagnostics, they also tested the battery health, which had been damaged from repeated deep discharges caused by the failing alternator. This is considered a serious repair since the charging system affects all electrical components. If left unchecked, it can lead to complete electrical failure while driving. The original battery also needed replacement due to cell damage. Proper diagnosis requires professional testing equipment to verify alternator output and battery condition. Would recommend getting it checked soon, as these symptoms typically worsen quickly and can leave you stranded.

Yes, that alternator issue sounds identical to what happened to my XTS. The voltage drop and weak starts were exactly the same. A failing voltage regulator turned out to be the root cause in my case too. Did you keep track of your repair costs? Would help me gauge what to expect. Also curious if youve had any other electrical problems since the alternator replacement and if the battery health has stayed good.

Following up on my earlier post, got the final bill and the power supply repair came to 290€, which covered replacing the heavily discharged battery. The mechanic confirmed the alternator issue was causing the voltage drop, but thankfully the alternator itself was still functioning properly once the battery was replaced. The undervoltage warnings have completely stopped since the repair. No more electrical problems with starts or dim lights. The charging system is now maintaining proper voltage levels. The new battery has been holding charge perfectly for several months, and all electrical systems are working as they should. Its been a relief not having to worry about getting stranded due to power failures. Would definitely recommend getting yours checked out soon, as these charging system problems tend to cascade if left unaddressed.

Thanks everyone for the input. I finally got my XTS fixed last week after dealing with those electrical problems. The symptoms kept getting worse so I took it to a certified shop. The technician found a failing voltage regulator that was causing inconsistent charging. The alternator issue was draining the battery, leading to those weak starts. Total repair came to 850€ including a new alternator assembly and battery since the old one was damaged from repeated draining. The battery health is now perfect and the voltage stays steady. No more dim lights or struggling starts. The charging system works like new, definitely worth fixing before getting stranded somewhere. Really glad I got it done professionally instead of trying quick fixes. The car runs great now with all electrical systems working normally. Should be good for many more years without electrical problems.