Brake light and battery light on simultaneously and intermittently

[montjim99]

1993 legacy wagon. Brake light and battery light come on at same time and then go away and come back again seemingly randomly. I tested battery with engine off and it read 12.7 volts. With engine on, it read 14 volts, but periodically while idling, engine would make a light click noise and the voltage would quickly go down to 13 and quickly climb back up to 14. And when I turned engine off, voltage went back down to 12.7 but after only half a minute or so went to 18 and stayed there for roughly 10-20 minutes before returning to around 12.6. Any advice appreciated. Thanks.

[johnceggleston]

sounds like the alternator may be going. check the battery cable connections, make sure they are clean.

and then go to the parts store and have them test you alt.

[ShawnW]

Have them test the battery too. Could be a bad cell or something moving around in the battery cells themselves.

[1 Lucky Texan]

almost certainly a bad alternator.

[Fairtax4me]

Check the nut that holds the cable on the alternator. Make sure it's tight.

Also check battery terminals and the main engine ground.

[porcupine73]

If it went to 18 volts at any point that is not good, definitely sounds like something flaky going on with the alternator.

 

The clicking noise, was that maybe the A/c cycling on and off?