I just bought my 2.5 X-Type a couple weeks ago. It is a 2005 with 31,000 miles on it. I noticed last night at stop light that my headlights are dimmer in neutral (it's a manual). I blipped the throttle and the headlights brightened up to a "correct amount". It is not a huge difference but it is definitely notice able. I want to put aftermarket HIDs in but I am afraid that they are going to die with all this flickering.

Is this a battery issue, an alternator issue, or a different issue all together.

 

Not many people have alternator problems with an x-type but battery, cables and belts are normal wear and tear items. Search for threads on testing each one. This is the order I'd check them in from easiest to hardest. Some auto parts stores will check it for you for free hoping most people will need a battery or alternator. However, they usually don't guarantee they're correct and you may end up buying more than you need.

1. belt
2. cables
3. battery
4. alternator

 

Mine did the same thing. This sounds silly, but check your PCV hose. I just replaced mine (it was split open about 4" - I don't know why the car ran at all!), and my idle is smoother and slightly higher on the tach, and the lights no longer dim at idle.

 

nViouSS, when you see the lights being dim, are you running a lot of electrical loads (ie, headlights, wipers, electric seat heaters, rear defroster, etc)? If so, you are simply seeing a byproduct of all the loads in the car. Try turning off the seat heaters and the rear defroster. See what the headlights do then. If they get brighter, then that is your problem. Our cars are built with a 160 amp alternator in them. But, it only outputs 160 amps when the engine RPM is up over about 1600 RPM. Below that, the alternator output drops in relation to the engine RPM (lower the engine RPM, the less output you will have). In short, at idle, you can only plan on the alternator being able to output about 90 amps max. Get the idle up to 1200 RPM, then you are looking at about 130 amps or so. Granted, this also assumes you have a healthy electrical system. If your alternator is starting to go, then you can see even less current than what is stated due to internal resistances in the windings.

If you want to know how to check this out more and prove what is wrong, let me know. I just need to know how you are with a multimeter. They are simple checks, but if you are not familiar with a multimeter, it can be intimidating.