Rainier's Voltage Drop Causing Multiple Electrical Issues

Had a similar issue on my 04 Rendezvous with all the classic low voltage symptoms you describe. Being somewhat familiar with charging system issues, I initially thought replacing the battery would fix it, but the problems persisted just like in your case. After dealing with flickering lights and unreliable starts, I took it to a workshop where they diagnosed a failing alternator and voltage regulator. The alternator was only putting out about 12V when it should have been closer to 14V while running. Total repair came to 290 for parts and labor, but it completely resolved those electrical gremlins. Before you replace parts, get the charging system properly tested. A multimeter can confirm if your alternator is outputting the correct voltage. The battery voltage should stay steady above 13.5V with the engine running. If it drops below that, especially under load, thats typically a sign of alternator issues. What readings are you getting from your battery voltage both at idle and while running? Also, are you noticing any unusual sounds from the alternator belt area? This could help pinpoint if its truly an alternator issue or something else in the charging system.

Just had my 136K service done and ran into very similar symptoms. The voltage tests at the battery terminals showed exactly what you described, significant voltage drop during startup and inconsistent readings while running. Turned out the battery terminal connections were actually the main culprit, despite looking clean on visual inspection. There was hidden corrosion inside the connectors that was causing poor contact. After proper cleaning and securing the terminals, most of the electrical problems cleared up. However, my alternator was also showing signs of wear and putting out lower voltage than spec. Had both issues addressed and now the electrical system is rock solid. If you are checking voltage, make sure to test both at the battery terminals and alternator output to isolate the problem. Worth having a professional run a full charging system diagnostic before replacing major components. Sometimes its the simple fixes that solve these electrical problems.

I agree about testing both battery terminals and alternator output. After fixing those issues on my Rendezvous, I actually ran into a similar problem again last month. The voltage regulator was failing intermittently, causing unstable power supply to various systems. A proper voltage test showed the alternator output fluctuating between 12-13V instead of maintaining a steady 14V. The battery terminal connections were good this time, but the voltage regulator inside the alternator was the problem. Rather than just replacing parts, I had a shop do a complete charging system diagnostic. The alternator issue was confirmed when they found it wasnt properly maintaining voltage under load. After replacement, the system now holds steady at 14.2V while running. No more flickering lights or starting problems. Always worth doing thorough testing first since low voltage symptoms can stem from multiple causes in the charging system. Quick voltage readings at different points while the engine is running can save time and money in diagnosing these electrical problems correctly.

Thanks for the detailed feedback on the terminal corrosion and alternator issues. I checked the readings again today, battery voltage drops to 10.2V during cranking and only reaches 13.1V while running, which matches what you described. Poor voltage output seems pretty clear now. I cleaned both battery terminals thoroughly and reseated all connections, but the electrical problems are still present. Given the age of the car and symptoms matching your experience, I will likely need that alternator replacement to fully resolve the low voltage conditions. Going to have a shop do the complete charging system diagnostic first to verify. No point throwing parts at it without proper testing. Thanks for helping confirm my suspicions about the power supply issues. Will update once I get the results back from the diagnostic tests.