Part store says dead battery and dead alternator? Best way to verify?

• Part store says dead battery and dead alternator? Best way to verify?

 

Some mid-grade scan tools have a battery and alternator test function, the Harbor Freight model will set you back about $100-150. I would assume the parts store used a similar scan tools to give your diagnosis.

A shop will give you a second opinion for whatever the charge for diagnostics.

If you have a decent multimeter, you can perform a voltage check, but that doesn’t always give a full diagnosis on what’s going on without putting the battery and charging system under a load.

A healthy, fully charged battery should show 12.5-12.6 volts at rest. The alternator can be tricky on newer vehicles because they can vary charge rates based on current draw… you should see greater than 12.5 volts when running, but that doesn’t guarantee the alternator is good. If the battery is discharging while running, that is an indicator of a problem, but not necessarily that the alternator is bad.

 

Youtube video shows disconnecting positive battery terminal while engine is running to test alternator.
Is this a thing on modern engines? Seems sketchy..

 

More likely one or the other. If its the alternator the battery is probably fine, and vice versa. Either way the battery is dead (but maybe not bad), so charge it and see if it starts.

 

This thread is being way overthought. To start with, don't listen to the idiots at a parts store. Most of them don't know anything about vehicles. How old is the battery? Being that you have a 2021, I'm betting it is the original battery. Most batteries only last on average 3 years before they start going downhill. I highly doubt that your alternator is bad.

 

I agree. My battery did not last 2 years. You can read probably 100 posts on here about similar experiences with OEM batteries. I would put a new battery in it. Start engine turn on all electrical components and then lights on high beam. If lights dim then you probably have an alternator issue.

 

The problem with the battery testing scan tools is that they are inaccurate. I put brand new batteries in 2 of our vehicles at the same time and my tester told me that they were both bad and failed the CCA test.

 

That's odd? My battery tester works great on standard lead acid and AGM batteries. I normally put a brand new battery on a charger before I put them in vehicles.

 

I replace car/truck batteries at, or about, 36 months. Costco Interstate 27F or 24F depending on vehicle. I'm just not gonna try and drag it out and get that last week/day/hour out of a battery. Let's call it: smart maintenance.

HIGHLY doubt alternator issues. HIGHLY.

Go get a new battery and truck on.

 

It is odd for sure, and its an Autel unit.

 

Here's the current status of my OEM battery on a truck with 27K that's not driven much. I normally full recharge monthly. Short drives won't cut it.

 

Most places don’t realize the alternators in these trucks are voltage regulated. You’re never going to see 14 volts on a warm truck. If you’re getting over 13 volts, then the alternator is fine.