Skip the auto shop - Our mechanics make house calls

Q: Alternator overproduces power above roughly 5,000 RPM, how badly do I need to replace it? Worst case scenario?

asked by on

2000 nissan Maxima, 165,000 miles Bought a used alternator around 150,000 miles

Basically pretty much only when I floor it (which is more often than your average driver for me haha) any electronics will go overboard for anywhere from a half-second to about two seconds tops. This includes the fans blowing harder, and the lights getting brighter mainly, and two lights will come on in the dash. It is fairly reproduce-able and not random. Could the ECU crash eventually?? : /

The alternator should not be putting more than 15.5 volts and 95 amps at 5000 RPMs. If the alternator is, then you need to replace the voltage regulator inside the alternator or replace the alternator. Make sure you have a battery that is fully charged and is good when tested with a load tester. If you continue to run the engine with the alternator above the 15.5 volts maximum (should be about 13.5 volts normally), then you may burn out components and it will cost you much more than a replacement alternator will. The ECU and other modules have protection for over voltage, but this protection may not provide long-term protection against voltage above the 15.5 volts may eventually burn out. I recommend having your electrical system inspected by technician, such as one from YourMechanic. They will be able to make a diagnosis and replace your voltage regulator or alternator if necessary.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  • Home
  • Questions
  • Alternator overproduces power above roughly 5,000 RPM, how badly do I need to replace it? Worst case scenario?

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: 86 GMC 305 quits firing occasionally

This car is very old. Personally, I'd just go and get a rebuilt distributor. Most companies sell the rebuilt distributors with the lifetime warranty. They don't cost that much. Replace your entire distributor assembly. If that doesn't fix it,...

Q: Buttery light on the dashboard

Hello. If the battery light is on then that usually means that there is a charging system issue. It is typically caused by a bad alternator, but it can also be due to bad connections or an electrical failure in...

Q: Car no longer turns right or left

The not turning left or right is due to the power steering belt is not turning from the cooling fan and leak issue. The fluid leaking sounds like the coolant is leaking from the water pump and/or radiator. If possible,...

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...
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...
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.