Hi, This problem you describe is usually a brush issue. When they are low or have bad contacts the warning light reacts to engine speed just like you’ve experienced. I’m not sure why this would happen to you in 2 years though unless it was a used part?
There’s some other things you can check, but it would be easiest to take your vehicle into a starter/alternator place and have them check it, around here they charge $10 to do this. They also sell the brushes you will probably need,… cheap! I paid $5 bucks for my last set for a honda alternator which was a solder in type.
If your going to do it yourself there are several scenarios that you might find…
Check the alternator field wire for battery voltage/corosion or loose contacts. If the voltage on the field wire is lower than 10.6v then a perfectly good alternator will not turn on and will not put out a charge and the battery light will be on. If this is the case and you have less than 10v at the field wire then there is a voltage drop somewhere. Check the Dash fuse box (Fuse 24 its a 15amp) where the wires come in at the back for fuzzy corrosion, and voltage. if you have battery voltage here, but not at the alternator then the wire to the alternator is bad (the Black/Yellow one). This is the wire that provides the current to the brushes, and may react to engine vibration and harness movements.
Also check the main battery clamps for corrosion fuzz and voltage drop, and the power wire at the alternator. If there is a voltage drop on the Alternator cable before it reaches the Main Fuse box (fuse 30, 70amp) Then the warning indicator should come on because the voltage regulator is not seeing the alternator voltage output. This is not likely because your problem reacts to engine speed… but if your stuck it’s something to check. This would normally have low battery voltage at the field wire, and 14v+ at the power cable going to the battery and the light would just stay on.
No problems with the wiring? again, I would NOT normally do the first step I mentioned above UNLESS there is no or low voltage on the field wire! I would check everything with a volt meter and if I got the same voltage on the alternator output cable as is on the field wire I would pull the alternator and continue below…
Take apart the brush housing and inspect the copper armature that the brushes ride on. They rotate with the rotor and wear slowly… slower than the carbon brushes which stay sationary, but they do wear out and can corrode if you wash your engine with unusual cleaners. A little grey scotchbrite pad can be used to clean them if it’s not too bad. At the same time your brushes will be visable, they are spring loaded (don’t loose the springs). under 1/4" left from the braided power cable, they don’t contact very well and should be replaced (you’ve come this far). New ones vary in length, but should be between 1/2" to 3/4" long. But if you have the new ones available you’ll know how long they should be. Also look at the carbon brush wear pattern… it should be clean and intact (no chips or missing parts) and should not be mirror finished or glazed. You can clean the brushes aswell with the grey scotch brite carefully. I wouldn’t use chemicals to clean the brushes because most automotive cleaners are designed to dissolve carbon.
This should help you find your problem… Good luck.