John1C

Drove the 2001 GS300 to a drive-through, had to wait maybe 10-15min. It was a pretty hot day so the AC was on full-blast and radio was on as well. After getting my food and starting to drive away, the radio cut out for a second or two and the battery light flashed for a second. Then everything was normal again. As I came the stop in the parking lot before turning onto the street, the same thing happened again with the battery light and radio.

Drove 8 miles home by freeway and local streets, and haven't had an issue.

So, based on the evidence, could it be an alternator or battery issue? Maybe the long wait in idle with the AC and radio on was the reason?

Thanks for your help.

iToaster

I'd say it's the alternator. The battery doesn't play much of a role once the car is running, but if the alternator can't provide enough power, the car will draw from the battery and turn on the battery light in doing so. Alternators aren't the most efficient at idle speeds, so if it was going out that's where you would start to see trouble.

Phillie

Or it could be bad conmection/s in the charging system. If you have a multimeter check the voltage and if you can amps while the car is running.

Ava92

iTrader: (3)

Hey i had the same problem on my GS4 when i first got it, AC on full, radio on pretty high, stuck in traffic and it just died.

I installed a new battery and it fixed the problem. I have since installed a sub and amp and still haven't seen any problems in two months.

If the battery is more than a few years old (or if you aren't sure of its age) it couldn't hurt to change it. I am no expert though

Advil4u

This may be a new 1 but take the belt off and check if there is any play on your harmonic balancer pulley I had mine go out recently and had the same symptoms..........if the pulley on the harmonic balancer is slipping due to stress from ac being on then for sure it is not spinning the alternator fast enough to give you the proper voltage needed while at a stand still not sure if tat makes sense

chubz

iTrader: (1)

i had the same exact issue and i thought it would be the alternator. turns out that it was the battery. the alternator keeps the car running and charges the battery which is what keeps all your accessories running ie. radio, headlights etc. take it anywhere and make sure it is charging at 100% . mine was charging about 75% so it couldnt keep up with the load of everythng and thats why things were cutting on and off.......i was also in drive through lol

bigegg

If you check the voltage across the battery terminals whilst engine is running, then again with engine off, it should tell you whether it is the alternator or battery.

Both should read 13V +
If engine ON voltage is low, it's probably the alternator (but might be the battery pulling voltage low)
If engine OFF voltage is low, then it's might be the battery - but could be because alternator isn't charging it.

Charge the battery with a charger - if battery will fully charge, then it's the alternator.

Chances are, unfortunately, that if your alternator is duff, the it will have damaged your battery

John1C

Well, took the car in to have it checked out just to be sure. Turns out to be the battery. Got a Lexus OEM battery. Let's see how long this one lasts.

Thanks for all the suggestions!

bigegg

Did you check the alternator as well?
Cos a duff alternator will kill your new battery.