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: Car won't move only buzzes when in gear and rolls in park.

Check the shifter cable to the transmission and see if it has broken off the transmission. The buzzing noise is the hydraulic fluid going around the main valve on the transmission and the valve is stuck in between a gear....

Q: Oil pressure went all the way t 0 while driving

The oil pressure will usually drop down to zero when one of two things are happening. Either the motor is in fact low on oil or the oil pressure sending unit is not working properly and may be producing a...

Q: partially engaged brakes

You will need to jack up the front wheels and see if the tires will turn freely. If both front wheels are binding then you should try to loosen the brake lines that connect to the master cylinder to see...

Related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.