The Lexus alternator is the electrical power source for your luxury automobile. When operating properly it should be producing over 13 volts of electricity on a steady basis. One of the best and simplest manners in which you can test the alternator on your Lexus is to start your vehicle up and allow it to run. With an observer in the front of the vehicle, the lights should then be turned on. If the lights are dim and or the engine seems to lose a little bit of power, then the Lexus alternator is not function at full capacity. If you are not sure of the result with just the lights on, then begin turning on other accessories that require electricity to run like the fan and power windows. If the alternator is producing less than 12 volts of power, with the more accessories are turn on, the limited power can be detected. The reason this test works is since each accessory requires 12 volts of electricity to run, they cannot function as expected without it. As more items are turned on in your Lexus, the power being supplied by the battery is being drained since the alternator is not producing enough. It is this limited supply being distributed that you can detect. If the battery is disconnected with the engine running, the effect is more dramatic and the Lexus could stall. The replacement of the alternator is simple. The drive belt has to be removed from the pulley and the battery disconnected. With the wires disconnected the mounting bolts can be taken off freeing the old part so the new one can be installed. Reattached the component and hook up the battery, then the system should be tested again.