I installaed new alternater, and battery in 1987 cavalier. Battery light still stays on, and alternater is not charging according to test light.but alternater is good.

Is the system charging? You should have 14.2 14.6 volts at the battery. The charge light is controlled by the alternator internally. If the charging system is working, you could have a bad diode inside the alternator keeping the light on or a short/grounded circuit to the battery light

Not good to pull cable off batteries to test alternators an yes could be alternator or u may not have power to the alt.meaning the wire on top of alt or may havy bad plug wire boyh easy to check

replace the negative terminal

Recharge battery from home, or take battery to supplier to see if it charges, when charged check dash to see if light is on when running, if there is a red light which might be very faint, get diode replaced in alternater, (or checked to see if it is charging) (lot cheaper than buying new alternater). Which most dealers will try and sell you.

You probally have a drain on the system as in glove box lite stays on ,, alternater not charging properly .

get a12 volt test light remove negitive cable from battery attach clip on test light to negitive cable removed from battery. touch other end of test light to negitive side of battery if light is on something in car is pulling power if light is off everything is turned off you can test this if light is off by turning on the headlights the test light should stay lit until you turn off headlight switch. If light is on when fistr connecting to battery turn every thing off in car or disconnect anything includeing trunk or under hood lights one at a time until test light is no longer lit. if this is not the problem load test battery.

so u have put a new battery nd alternater on there?there is 2 fuses u need 2 check there is an alternater fuse nd a battery fuse u need to check

Take it to a mechanic.

u may have parasitic load what that is when like somethin on the car stays on even if u shut everything off causing to drain the battery

Mazda Mpv 2000 I also have the same problem, the alternater is testing good- 14.12Amp, so what is the problem the battery light will not go off.