My 1999 Lexus GS400 occasionally(maybe 3-4 times a month) makes a fairly loud vibrating sound which seems to be coming from the lower dash or console area that lasts for 10-30 seconds or maybe a little more. It is definitely not the radio and does not seem to be related to having the air blower on. It is in very good shape overall and has almost no air or rattle noises. Any suggestions for what might be causing this?
Any other vibrations, like the steering wheel or accelerator pedal at the same time?
Does this vibration take place when the engine is idling and the car is parked?
Does it take place at city driving speeds?
Does it take place at expressway speeds?
Does it take place under all of these conditions?
You have a failing HVAC servo motor.