Q: Need to know if my alternator is bad.

asked by on

Going down the road I noticed that my battery gauge was all the down passed 9 volts. Went further and all my gauges stopped working including my Windows and locks all electronic. Go home and left it running and disconnected positive cable from battery and truck died. Took altnator off and had it tested and it tested fine so I took battery out and had it tested today and it was fine too. So now I don't know. I thinking that the regulator on altnator my have gotten stuck and when taking it out made it in stuck?? I really don't know.

My car has 190 miles.
My car has an automatic transmission.

Hey there, thank you for asking about your 2005 Chevrolet Silverado 1500. Disconnecting the battery while the vehicle is running can damage the Powertrain Control Module (aka, vehicle "brain" or "engine computer") or other electrical components due to voltage excursions (excessive high voltage due to the sudden disappearance of the battery as a load). I (and vehicle manufacturers) wouldn’t recommend using that approach if the problem recurs. Not all alternator failures will show up using box store testing machines. Starters are notorious for this. Your starter could be totally non functional due to a worn Bendix drive and yet when you test it on the store tester, it "passes". Heat and load affect the alternator when it is in a running car so it remains to be seen what your results will be. You can easily test at least the output voltage of the alternator on your running car, which you should do now for reference and again in the future if the problem redevelops. If charging voltage of your alternator, as measured on the car, is out of spec now, I would replace the alternator now to avoid future problems. If you would like a mechanic to do this for you, have a certified technician from YourMechanic replace the alternator in your car.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Need to know if my alternator is bad.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: I am looking for window regulator and switch for Acura TSX 2005 passenger size. How much it will cost me?

Hi...both of these repair services are available. To obtain an exact quote for the window regulator repair or replacement, please click on "Get a Quote" at YourMechanic's window regulator repair service page. Similarly, to get an exact quote for the...

Q: Four-wheel drive encoder motor not working properly.

Hello, Since this recurring regularly the vehicle should be scanned for code. There is a good chance that the wiring to speed sensor on the transfer case has become compromised over time and the wiring harness needs to replaced. This...

Q: Check engine light not working.

If the check engine light is not coming on, then that is a good sign. If your dashboard before displayed the check engine light before and now it is not coming on, then the dashboard warning light could have burned...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...