Skip the auto shop - Our mechanics make house calls

Q: battery voltage falls when engine fan kicks in

asked by on

I changed the battery out of the vehicle today, I had a dead truck Friday, boosted it and worked fine for 2 days, died again on sunday, deader then dead. so I went in and bought a battery. Now my problem is when the truck is started and I turn the a/c on or the fan the truck is darn near ready to die, but doesnt happen when the radio is on, this is scary - nor do I feel comfortable driving it anymore. Would it be the alternator or? I have a diagnostic machine and it says there is nothing wrong with my vehicle. I am at a loss on what to do.

My car has 14300 miles.
My car has an automatic transmission.

A: The alternator may not be charging; when yo...

The alternator may not be charging; when you put the fan on, it could be drawing too much power so the engine needs to stay running and will stall and kill the battery if battery gets too low. Check the alternator output with an amp meter, and you will likely see that it is not charging.

It may be a good idea to have a qualified mechanic inspect your loss of power condition.

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!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Temperature gauge sits on cold always

This is a common issue on this generation of the Chevy Malibu. This could be any one of a few problems. This could be a result of a bad BCM (Body Control Module). This is a module in your car...

Q: Vehicle leaking after repair

Hi, what color is the fluid? Engine oil will be brown or black depending on how old it is. Transmission fluid can be red or brown and thick. Coolant tends to be yellow or green and will feel similar to...

Q: My gas cap replaced still no click

Having your gas cap not work correctly can be a frustrating experience. It appears that the concern with your Ford Escape may have something to do with the fuel filler neck not allowing the new factory gas cap to be...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
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...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...