I just had the water pump, timing belt and other drive belts replaced by my Toyota dealer on my 1999 4Runner.
Now when I have the truck in gear (D or R) and turn on the healights, I get a high-pitched "chirping" sound from the engine compartment. Turn off the headlights and the sound goes away. Turn on the fan inside the cabin and the sound returns. Put the truck in "N" or "P" and the sound goes away.
I'm sure its some belt that's too tight, but which one?? Alternator, timing, etc...
This only happens when I put some load on the engine (headlights, fan motor, etc.) with the car in gear.
Anybody know?