Q. What is the easiest way to replace high-intensity-discharge bulbs in my 2007 Infiniti G35X? The headlights rotate right to left with steering. Do I have to take off my front bumper and remove the whole headlight assembly?
A. Do you actually have HID bulbs, or do you have the standard xenon bulbs?
I ask because the optional HID bulbs should never need replacing - which is good, because they are really expensive.
This is important because replacing the xenon bulbs is easy. It is so easy, in fact, that there is no procedure. The normal xenon bulbs are not even worthy of a replacement procedure in the manual, in short, so the process must be pretty simple.
There's a rubber or plastic boot on the back of the headlight assembly, inside the engine compartment. The wires that energize the bulb go through the middle of it. Unscrew it from the housing, and there is your bulb.
Install the new bulb or bulbs without touching them with your hand, because the oils in your fingerprints will crack the bulb when it heats up. Use clean cotton gloves or a hanky to install the bulb in its socket, then reinstall the gasket/bulb socket assembly.
The warranty book says that it should take less than half an hour, and that includes enough time for the mechanic to walk out into the parking lot, get the car into the shop, change the bulbs and drive the car back out to the lot.
Q. In February 2006 I purchased a new Mercedes-Benz E350W. I have returned the car to the dealership six times, complaining of hard shifting into first gear and the occasional failure of the transmission to shift out of first gear after start-up.
Updated software was added during each of the first four visits for service. During the fifth visit a new valve body was installed with updated software. That valve body was replaced with a newer version, with updated software, during the sixth visit.
I drove out of the dealership's parking lot after the sixth visit, and the transmission immediately hung in first gear. So I now have returned the car for the seventh time, with no evident resolution of my problems in sight.
I have noticed on the Internet that other owners of the same model and year are experiencing the same problems. Is there something the dealership is overlooking? They say that they find no code in the onboard computer that indicates the malfunctions.
A. I haven't seen any buzz on the Internet about your specific problem, but you may have spent more time on it.
It's time for you to start making Lemon Law noises. Basically, the dealer has a reasonable number of attempts and a certain number of days - which varies from state to state, so your mileage may vary - to repair anything covered by the warranty. If he can't or won't, you can force him to replace the vehicle with a comparable one or to buy it back.
Trust me, neither you nor the dealer will be happy if this process goes to arbitration, which is usually how it is resolved. The dealer is entitled to a reasonable sum for any use you've had of the vehicle. This usually takes the form of a cost per mile, and it is not cheap.
At this point I'd start squawking for a new transmission under warranty. If they won't go for that, you don't need to write back to me - you need a lawyer.
Q. I have a 1967 Chevrolet Nova SS I rarely drive, but I do start it up once in a while.
Last week, after starting it in the garage to let it run awhile, I noticed that the fuel gauge went from a quarter of a tank, which is correct, to clear across the gauge and pegged beyond the full mark. It remains there even when the ignition is turned off.
Can you tell me where I might start looking for the problem? Is it the sending unit?
A. Judging by the age of the car, I'd guess that it's the sender. I don't even have a schematic for anything that old handy, though. Get out the voltmeter and start chasing it down.
Mike Allen is a senior editor for Popular Mechanics magazine. Questions should be sent via e-mail to driveit@nytimes.com.
