HID Dim/flicker on startup
 

Hey everyone. I bought my car used, and it had HID lights installed. I have loved them the past 2 years, but I am having an issue now. Having not installed them myself, I am unfamiliar with common issues/general knowledge about HID's as a whole.
The issue I am having, is that upon startup, the drivers side bulb will flicker for a while, and then when "warmed up" is significantly dimmer than the passenger side. I can see that its on (it's lighting the lens) but its output to the actual road is... well it may as well not even be on.
My question is, do HID ballasts go bad over time, and are these signs of such a thing happening? If that is the case, an additional question: Do ballasts have to be matched to the bulb? Or, if these ballasts worked in this car, with these bulbs, would any ballast be acceptable so long as it is meant for this car? (meaning that the intended bulb wattage would be the same for one ballast to another).
I am contemplating getting the spec D headlights in the spring, so the reason I'm asking is, If I buy a D4s HID kit for intended use with the spec D headlights in the future, will using the included D4s ballasts with my current H11 bulbs be possible?

Sorry if this is a bit long and Rambly, but thank you in advance for any help.

Cheers!

Bulbs do go bad over time

The first thing I would do is check the quality of the electrical connections that were made to retrofit the kit, including the ground (earth) connection. The ground should be attached to a part of the body that isn't painted or otherwise coated. Any wire splicing should be securely connected, preferably with T-taps. If it was soldered, the joints may be failing due to heat generated by the engine (not necessarily true if the wires are placed in a cooler part of the engine bay).

That said, HID ballasts can go bad, particularly if they aren't made by a reputable manufacturer. If the wiring looks good, switch the driver's and passenger's ballasts and see if that fixes the problem on the bad side.

If all that doesn't yield any clues, the bulb is likely going out. Not sure about ballast/bulb compatibility, though, sorry.