2007 Toyota Tundra 4.7L - Stopped Running, Won’t Start
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General Information:
The vehicle was towed into the shop with a no start. There were no lights on the dash when the key was turned to the on position. Customer came in and explained that the truck died going down the road and before if quit, all the lights started to flicker.
First Thoughts:
It seemed like a classic dead battery and alternator. I’ve done one before with the same symptoms.
Diagnostics:
Diagnostics for checking an alternator are fairly simple, they can get complex, but most of the time, they are simple. The general rule is around 14 volts with the vehicle running. There is one test with loads and one without loads on the battery. Loads for a vehicle include the low beam and high beam lights, a/c compressor, blower motor, etc. Basically they are things that heavily use the battery.
The truck was completely dead, so I grabbed the jump box and cranked it up. I removed the jump box after the truck started and it almost immediately went dead. So I cranked it up again and kept the jump box on the truck while I checked the output on the alternator.
The tool I used to check and see if the alternator was charging is a Power Probe. I believe the one I use is the 3rd generation. I have been using it for years and highly recommend it.
The Power Probe said the alternator was not charging.
Usually mechanics just call it right there and say it needs an alternator, but it’s always a great idea to take an extra few minutes to test the other factors of the charging system.
The other factors may include:
Fuses to the alternator
The main positive stud on the alternator (I’ll explain a little later)
The battery terminals
It’s a possibility that a dirty battery terminal might cause an alternator to seem like it is not charging. It’s important to thoroughly clean the battery posts and cables and then test the alternator again.*
* Don’t shock yourself, just let a professional do this stuff….
If you suspect that the alternator is good but maybe there is a broken wire or corroded terminal that is stopping it from reaching the battery, try checking the positive lead that is directly on the alternator. If you have around 14 volts while the vehicle is running, it’s a possibility that you have a wiring or corrosion issue.
*For real, just let a professional do this stuff. You don’t want to get hurt.
After I checked all the above, I determined that it was definitely the alternator that went bad.
I replaced it, and boom, charging like it’s suppose to do.
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