I tend to get a lot of automotive questions. Once someone finds out that I used to work at a dealership they like to ask all kinds of interesting questions. I’ll try to log some of those questions, and the preliminary answers. I’ll call these “Diagnosis by phone”, since you can’t diagnose it over the phone and that’s what some people want you to do. I’ll also try to follow up with a final answer/diagnosis if I get to work on the issue and solve it.
Here’s one that I got just the other day.
I went to start my truck this morning & it just went buzz, buzz. Does that mean the battery is dead? It started right up after sitting all yesterday in the unsheltered parking lot.
Instead of giving a direct answer I start with a few of my own questions:
What vehicle? 2002 Toyota Tacoma (V6, A/C, 5-speed, 4×4)
Is it garaged? Yes
Has the battery light come on by itself or in conjunction with the brake light?** Not that I’ve noticed.
Has the battery ever been replaced? No, and I bought the truck new in 2002.
Diagnosis by phone: Battery needs to be replaced (75% sure). There is a chance that the owner did not notice that the batt light was on and the alternator is bad.
Final diagnosis: Battery static voltage was 10.25V. No excess corrosion on either of the battery terminals. Hooked up the battery charger. At 2 Amp charge the battery takes 5A. At 15 Amp charge the charger flickers on and off. Started the truck and the battery is getting 14.4 volts from the alternator. Alternator good, battery bad.
Solution: Replaced the battery. Starts better and faster even in the cold. After pulling the battery I also noticed that the sides of the battery were bulged. Another clue that the battery is bad. Replaced battery, everything is good.
** Typically on a Toyota when the Battery light and the Brake light both are illuminated at the same time the alternator is not charging.