Have a 2007 Camary XLE, 2.4L with 126k miles on it. It originally was my company cat which was purchased new my the company and I’ve driven since then but recently bought when I retired. Car has been well maintained with little issues.

the past day or so, while driving the battery light popped on, stayed on for a couple of minutes then went off…I was puzzled but thought possibly a belt slip. Yesterday while driving the same thing occurred and I drove directly to Autozone to have the charging system checked. Was told the alternator was only putting out 12.3 volts and diode were bad. The lady also told me my starter was bad, but battery was good. I bought a new alternator and on the way home stopped at ORiellys and had them test the alternator as well with the same results. Went home installed the new alternator and took back to AZ to make sure the problem was corrected. The new alternator tested bad as well on my car, low voltage. I then took the original alternator (core) into the store and the guy bench tested it and it was putting out 14.0 volts when on the car it had been barely 12.

Thoughts? Belt? Tensioner?

 

Unless the belt is grossly loose doubt this would be the issue. If this loose one would feel it.

How did the stores check the alternator?

Get your own voltmeter and DIY to check the voltages. Engine off battery should be around 12.9V. Engine at 2000 RPM 13.5 to 15.1V.

One can buy a voltmeter that plugs into the cars power outlet to view voltage when driving.

https://www.google.com/search?client...plug+voltmeter

Or get a cheap OBDII scanner that can read alternator/battery voltage

Check the battery cable connections for corrosion, loose wring, loss negative battery cable ground bolt, issues with the alternator electrical plug connection, etc. One time had the screw connecting the plus battery cable to the battery terminal loose causing all kinds of electrical issues.

Has happened the el cheapo rebuilt alternators can be bad out of the box.

 

So, I got the volt meter and when at idle (which was some what stumbling) had 12.7 or so volts. When it was revved up I had around 13.7 or so. Leading up to all this I recalled that the evening before this all started I’d bought gas at Meier and wondered whether there was some connection. I purchased a bottle of Techron Fuel System Cleaner and put in another 10 gallons or so of gas. I drove around for awhile and my idle improved as did the overall performance.

I know this might sound odd but I’m now thinking the gas (we’ve had a ton of rain here recently) was the issue and thinking back the battery light popped on during deceleration as the idle RPM were very low….is that possible? All I can say is this evening the car is running fine.

Thoughts?

 

Disconnecting the battery will result in the engine computer needing to relearn what the idle should be. The result can be erratic or low idle. A good battery should be able to pick up the electrical load when the idle is low or decelerating.

Perhaps the idle speed worked itself out and not the cleaner. The original alt may have been bad.

If the issue reappears suspect wiring, loose or bad electrical connection.