battery warning light on after replacement

Sounds like an alternator problem or wiring issue. The battery/alternator light is not driven by a computer. There is nothing to reset.

How good are you with a multimeter? Can you read a wiring diagram? You may be able to do some basic wiring/voltage checks.

Anyway, recheck your battery connections. There is a small red wire coming off the positive terminal of the battery (as well as the big one). Make sure it hasn't broken. Alternator wiring is also known to break near the alternator connector. Do you have any way of lifting the car to check underneath?

Any auto-electrician should be able to help you if you tell him where everything is (connectors, etc).

What year is your car?

 

Was that battery light on before you changed the battery?

If the light was off before and you just changed the old battery, there's a little sensor wire which goes onto the positive terminal. If you didn't attach it properly or if the wire is corroded (which is generally is) it will throw the battery light.

Might be also worth checking if the small ground wire under the body is damaged or not.

If the light was on before you changed batteries, when car is running, get a volt meter and check voltage across the terminals. It should be at least 13.5V, if less than 12V then your alternator is not charging which will also throw the battery light. This will be the more expensive fix chances are alternator will need a rebuild or replacement.

 

Or if you've put the wheel arch cover back on and have put the wheel back on, check the voltage on the engine bay battery bus bar (right hand side under a plastic cover with a red "+" on it)

OR... buy one of these

https://www.ebay.com.au/itm/353934048871?

 

Here's the little red wire which sometimes breaks

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Sounds like the alternator is not charging the battery.
Put a voltmeter on the battery and measure the voltage with the car running, then turn the headlights on, the voltage should stay the same and not drop.
The voltage should be up around 14V. Engine off the voltage should be 11.5-12V...

 

11.5-12V is very low. Healthy battery should have ~13 volts immediately after the engine has been switched off and stabilise at ~12.6 volts a couple of hours later.
11.5 V means the battery has only 10% of charge
12 V means the battery has 40% of charge
Keeping the battery at so low state of charge will cause its accelerated sulfation and premature failure.

 

I made an error in my post, I meant to say, engine running and alternator not charging, the voltage could be 11.5-12V......

 

Certainly sounds like the alternator.
They use a Denso with a 3 pin connector.
Unplug the connector and check that you have a battery positive in one of the 3 wires.
Then turn your ignition on and make sure you have an ignition signal there as well. The third wire is the warning light.
As long as you have those three voltages there, the wiring will be good and you have a faulty alternator.
They are easily rebuildable. The regulator is readily available. A standard Denso IG-S-L regulator is standard in them - Transpo do an equivalent - IN220 part no.
The rectifier is normally what fails, and it is also easily replaceable.
Any auto Elec will be able to do it for you.


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Depends on the year of the car, I believe pre-1992 they use a Delco Alternator, worth investigating before assuming...

 

?
A pre -92 355?
That’s called a 348.


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LOL, I'm a moron aren't I!!
But everything you say is right, most likely a failed rectifier or regulator.....