Why is my alternator light flickering and sometimes staying on?

Good morning,

It sounds like a diode has failed inside the alternator causing the light to flicker as you see.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

https://www.2carpros.com/articles/how-to-replace-an-alternator

It can still charge but send AC voltage to the battery.

Check the actual voltage at the battery with a meter. It should be 14 to 14.5 volts DC. Then change to AC volts scale and see what the reading is.

Roy

My dc voltmeter shows 14 volts, but I haven't put it on AC voltage and tested it like that.
Will it mess my meter up by testing on AC Voltage? thanks

Not at all. It is a standard test all technicians perform.

Roy

I will try to get that done today.

Sounds like a plan.

Let us know if you have any other questions.

Roy

Will let you know the results. I have another question on this same car and getting ready to post it on a gas pedal position sensor.

Okay, I will be looking for it.

Roy

already posted it.

I put the voltmeter in the ac voltage range, and it started off in the 160 volt and started climbing one volt at a time and when it got to 170 ac volts, I took the probes off, but the voltage was still climbing higher. I wasn't sure how long you wanted me to keep the probes on the battery in the ac volt range.

The ac voltage would go higher and drop back down to like 50 volts or less then back up high then back down again.

Replace the alternator.

You have a bad alternator.

Roy

What should the ac voltage looked like when I tested it ?

My DC voltmeter in the car shows 14.0 volts.

Ac voltage should be 0. Anything above that indicates bad diodes.

Roy

Does that apply to all alternators on vehicles no matter what the make is?

Correct. There should be 0 AC volts coming from the alternator.

Roy

You taught me something there and I appreciate it.
Could I buy the diodes and put them in myself, I have some electronic knowledge ..

They are pressed into the diode trio assembly.

If you could find them, yes, you could replace them.

Roy

Doesn't Ebay or Amazon sell alternator rebuild kits ?

No clue. I would never consider rebuilding one. I replace them and then I have a warranty.

Roy

okay, thanks.

You are welcome.

Always glad to help.

Let me know if you have any other questions.

Roy

Roy, let me tell you what I tried.
I started my 1997 Nissan Pickup up and put my voltmeter across the battery terminals like you ask me to do to my 2005 Toyota Camry.
I set the voltmeter to the AC voltage setting just like I did on the Camry and the voltmeter showed roughly the same voltage as the Camry, the ac voltage went up to about 180 volts an dropped down some and right back up to a high voltage.
It never showed zero volts.

Based on your readings, you need an alternator for the Camry.

I don't know what else to tell you. There should be 0 volts of AC when the engine is running.

Roy

Thank you.

You are welcome.

Roy

I looked at it today where the hot wire connects to alt. it got hot and melted some insulation off and when I attempted to take the nut off the mounting shaft broke.

Did you disconnect the battery first?

Roy

yes.

Okay, you will have to replace the wire end and then replace the alternator. Too much current flow from the old alternator caused that.

Roy

Roy, now today I had the voltmeter set on AC Voltage and it read 30 volts. why is it reading this amount?

Okay, it does not matter at all. The fact that it has more than 1 volt says the alternator is no good. You need to replace the alternator.

Roy

Anytime my friend.

We are here to help.

Roy