Celica Forums General Discussion General Whining Noise

Hi everyone, I am new to the forum and would like to ask some advice.

On my 7th celica, I started hearing a whining noise coming from under the hood. It goes louder as I revved the engine and also being amplified on the audio equipment.

Searching the internet there are some information suggesting it is a failing alternator.
I put a new battery just to find out if it is the one causing the noise interference in my audio but it did not make any difference.
I tested the voltage when engine is not running and measured 12V. With the engine running on iddle voltage still the same at 12V. When I revved to about 2-3k rpm it goes up to 13V.
Info from internet suggests in should measure about 13.8-14.2 with the engine running.

Any advice would be much appreciated.

How many miles is on the car?

Has alternator been replaced?

Even in idle, alternator should be charging the battery at 13.5 to 14.5 V. If it stays at 12V, that means it's not charging and the alternator is bad.

It's possible the alternator is old, brushes have worn down too far to touch the commutator. They only touch and charge the battery when engine is driven at high RPM. The whining noise may be bad bearings inside.

My 2002 GTS' OEM alternator after 20 years 320K miles had totally worn out brushes, not touching the commutator and just stopped charging one day. The winding and regulator looked OK. I bought the brush replacement kit for $6 in eBay, install with only 3 small bolts. Worked great again.

If you can, remove the alternator and have a part store test it for free. If it's not charging, remove the brush assembly. You may be able to fix it for very little money.

The car has done 179k.
I had the car for about 11 years and during that time I have not replaced the alternator and it looked like it is still the original part.
Thank you for the information you shared, I will start investigating the unit. I did not know that there are parts you can service inside. That would be a lot cheaper that buying a new one.

Just a quick update that might be useful for anyone having same issues.

The noise was indeed caused by a dying alternator. After fitting a brand new unit all noise disappear including interference on the radio.

The voltage reading on idle on the old one is 12V all the time and now increased to 14V so battery charging is also improved.

@CAPTAINSOLO-Thank you for pointing in the right direction. Very happy the car is now running quiet as normal.

Looks like the bearing inside alternator is broken so it whines and not charging enough voltage.

Glad you solved the problem.