My bulbs are still working, but they just don't seem as bright as they used to be so I was thinking about getting some new bulbs. I have a few questions for those of you who may be familiar with the HID headlights:

First, I see that the bulb is a "D2S" I'm assuming that I can just install any D2S bulb in there and it should work. Is this correct?

I was thinking about buying these bulbs from dealextreme.com They are only $16 for the pair with free shipping. I know that's dirt cheap compared to the factory bulbs, but I figure at most I'll be out $16 if they don't work.

In regards to the ballasts, should they be replaced at the same time? They appear to be working fine, but if they could be causing my lights not to be as bright as they used to be, I'd like to replace them at the same time. On the other hand, if a ballast is a ballast and there's not need to change them, I'd like to save the money and not buy them.

 

They are not the correct bulbs, D2S are only if you have a conversion rather than OE, there is a specific connection at the bottom of the bulb, which only OE will fit, there are copies now out there that you can buy but from jaguar they are $150 each, the ballast module you can get but the cheapest I have bought is $450 the pair, the ballast modules are also fitted into various other manufacturers vehicles so not too hard to find on there own.

I have found correct aftermarket bulbs on Ebay in the past around the $50 mark, but they have a large square metal block on the bottom.

If you do have a conversion, then there is a huge variety

 

That sucks. I have the factory HIDs.

That brings up another question... If the problem is that the connector on the bottom of the bulb doesn't match the factory connector, then can I just get these bulbs and then replace the ballasts with ballasts that have a connector that matches the bulbs? Basically, I'm asking if these bulbs will fit in the lens on the Jag without modification. dealextreme.com also sells ballasts for $15 each with connectors that match these bulbs. I'm thinking that I could replace the ballasts and bulbs and have everything work as long as those bulbs will snap into the Jaguar lens properly.

 

Hmmmm the bulb mounting is very different from a standard H1 which the D2S's replace in a HID conversion, you would also have to change the plug going to the ballast as well coming out and going to the plug.
You would almost be better off changing the headlamps to standard and then doing a conversion, but even then the plug going to the head lamp is different.

It is a whole can of worms.... the reason I know this is beacause I did look into myself once to help a customer out, in the end I got him another xenon lamp unit from Ebay.