battery light on, -not the alt though...?

[the great him]

so like the title says, my bettery light has been coming on randomly for the last week or so, and is not more on than off, but im still charging at 14.5+volts, and the battery will consistently sit at 12.8v with no drop in a 24hr period with no use or sustainment.

i have already ordered the CS144 and the adapter/converter plug so i will be upgrading to that when it comes in. at that time i will also do the big 3 as well.

does anyone have any ideas or scenarios i could check, im not too good with electrical trouble shooting but i can do the work, just not the brain power side of it. thanks in advance for any input or help

 

[IBallEngineer]

Well here goes, speaking from some old experience, you are most likely incorrect about your alternator. The IC circuitry is most likely at fault. You are charging, but the regulator is malfunctioning.

In the old days the Battery light grounded through the stator output of the alternator and when engine started the output effectively took away the ground and the light would go out.

These days this is done through the regulator.

Personally I don't like to see 14.5 volts, but Toyota says as much as 15.1 is OK at 2000rpm and 77 degrees F. At idle you should see about 14.2 or 13.9!

Since you will be changing it anyway, clean all your connectors and you should be fine.

:couch2:

 

[LittleCaesar]

I'd say clean all the connectors as well, starting with those at the battery.

If you have ten minutes to spare, perform a voltage drop test on the charging system. It would give you a good idea if you need to replace the existing cables:
Voltage Drop Testing

Do you have a way to check the voltage (ex: Scangauge) when the battery light comes on?

 

[EatonKyleH]

There is a fairly common issue with the battery lamp wire breaking just before the plug at the alternator or making a poor connection which causes the light to illuminate but will still be charging normally.

some little testing info for ya.

1. Disconnect the alternator connector and check to see if there is battery voltage at all three wires. There may be a slight difference between the wires but they should be within a few tenths of a volt.

2. With the connector connected at the back of the alternator start the vehicle. All three wires should come up to charging system voltage. The Yellow/Green wire for the lamp control should come up to charging system voltage too.

if the light is not currently on when testing try wiggling the connector and harness near the back of the alternator and see if that will get the light to go on/off confirming a connection/wire issue.