Corolla Overvoltage Problems

I had a similar issue with my Corolla. Are you sure the battery connections are clean and tight? A bad connection can cause all sorts of weird electrical problems. Have you load tested the battery? What voltage readings are you getting across the battery terminals with the engine running?

Thanks! I checked the battery connections and they're clean and tight, but I haven't done a load test. Where should I measure the voltage and what readings would be a problem?

Measure directly at the battery terminals with a multimeter. You should see around 12.6V with the engine off and around 14V when the engine is running. If it's significantly higher, it points to the alternator overcharging. Given the symptoms, it's best to get it properly diagnosed at a workshop. Overvoltage can fry sensitive electronics.

Understood. Thanks for the advice to get it professionally diagnosed. I'm taking my Corolla to a workshop for a checkup. I'll post what the problem was when it's fixed. Thanks again!