Q: Car unexpectedly powered down while driving.

asked by on

Car had just returned from mechanic after getting new alternator, AC clutch, and various belts/valves replaced. Car drove great for about 20 minutes at 70mph, I slowed, and started accelerating again and the car began to hesitate/skip around 20mp to the point that I pulled over and then the car shook a few times and then powered down completely. Gave it a minute and then started it again and it drove great to 60mph and then started to lose it again and slowly dropped to 50mph and started to shudder again, pulled over, shook again, and then powered down completely. Car would not restart, it would turn over, but not catch. Prior to going to the mechanic, car was doing fine in terms of actual driving, never shut down or anything, my brake and battery lights would just flash intermittently and thus alerted us to an alternator issue. The catalytic (?) converter replaced in the last maybe four years, but my mechanic suggested that as a possibility though he can't look at it for a few days.

My car has 165000 miles.
My car has an automatic transmission.

I would suggest having the alternator checked to determine if it is receiving the proper amount of voltage from something called the voltage regulator. The voltage regulator regulates the charging voltage that the alternator produces, keeping it between 13.5 and 14.5 volts to protect the electrical components throughout the vehicle. The voltage regulator controls the field current applied to the spinning rotor inside the alternator. When there is no current applied to the field, there is no voltage produced from the alternator. When voltage drops below 13.5 volts, the regulator will apply current to the field and the alternator will start charging. When the voltage exceeds 14.5 volts, the regulator will stop supplying voltage to the field and the alternator will stop charging. This is how voltage output from the alternator is regulated. When the voltage regulator is not working properly, this may cause the alternator to allow the power the alternator supplies to drop resulting in the battery dying again. I would suggest having a professional from YourMechanic come to your location to diagnose and inspect your vehicle.

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. Car unexpectedly powered down while driving.

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: How many hours does it take to replace the head gasket?

If a car engine has overheated, the time and cost involved in replacing a head gasket depends on whether the existing head and block are serviceable. A complication is if the overheating was severe, the head and block might have...

Q: Q: How do I use the turn signals?

Turn signals are an important safety feature that alerts surrounding drivers when you are planning to turn. To signal a right turn, pull the turn signal lever (located on the left side of the steering column) up to the second...

Q: I hit a curb going about 20-30 mph while turning and got a flat tire. While getting ready to change the flat and put a doughnut on

Hi There, It may be difficult to tell what the light colored fluid could be as there are a number of fluids in the vehicle that serve various purposes. It may be likely that the light colored fluid may be...

Related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...