Possibly the alternator bearings are going out, the belt might be adjusted too tightly, or another device powered by that belt could be going bad. The water pump is commonly powered by the same belt as the alternator, and the bearings in the water pump could be intermittantly siezing up momentarily. Check all pulleys used by the alternator belt, except the crankshaft pulley, to make sure that they turn freely, have no play, and do not grind when turned. When installed, the belt should have about 1/2 inch (12mm) free play along the longest reach of the belt. If there is not sufficient play, the belt will break very quickly, and all components driven by the belt will be damaged.
It could be dirty fuel injectors.
A failing alternator.
Check bulbs or wireharness at back of bulbs.Switch handle that turns lights could be bad Toyo joe
This is the best advise you will get. go to a Toyota dealer (Not any aftermarket parts store) and but a Toyota reman alternator. If you put an aftermarket alternator, you will have problems again. That's good advise from a former Toyota technician. Good luck.
bad or going bad alternator belt
A bad belt, a bad regulator in the alternator or bad brushes in the alternator.
Low refrigerant charge?
Most likely the cause is a bad connection in that particular electrical circuit. There is a lot of time involved in trying to find exactly where that bad connection would be. Not worth fixing, in my opinion.
Defective alternator or internal voltage regulator is bad.
Bearings can fail or a diode can burn out. Age is the enemy of an alternator.
What causes the generator to burn out after replacing the alternator
Defective alternator or internal voltage regulator is bad.