Downgrading CTS-V HID headlight assemblies to halogen, then upgrading them to aftermarket HID.

  If you've seen many 1st gen CTS's around, you'll notice one thing in common.  They almost all have horrible oxidation on the headlights.  Its so bad that it may not polish out.  So, after trying the polishing route, you start looking for replacement headlight assemblies.  For a regular CTS, they're usually cheap.  $250-300 for a pair of aftermarket halogen assemblies.   For a CTS-V with HID's?   Try $995.  Each.  That's not a misprint.   Looking around, you can get them for $770 or so.  Each.   

Yes, this was an expensive car when it was new and expensive cars have expensive parts.  But, now?  Its a performance bargain.   And no, I'm not spending $1500 to $2000 on headlights that may get more sun damage in a couple years.

So, what's the solution?  For me, it was downgrading to halogens, then upgrading back to aftermarket HID's (because I liked having them).  I couldn't find anyone that had done this and was even told that you couldn't do it.  I was prepared to have to study wiring diagrams and replace connectors, but it turned out to be fairly easy.  It cost me about $275 for the headlight assemblies and $200 for a nice aftermarket HID kit.  Still not cheap, but better than the alternative.

Here's what you need to know to do this mod:

Tools:

10 mm wrench and ratchet

flat screw driver

phillips screw driver

1-1/8" hole saw (may be different for your HID kit) and drill

2 short (6" or so) sections of plumber's strap (or similar) and 4 couple washers/screws (I used screws from drywall anchors)

hammer

dremel or similar

1.  Find a guide to installing CTS headlights.  The factory service manual has instructions, or you can use these like I did:

http://www.cadillacfaq.com/faq/answers/bumperremoval/index.html

Remove the fender liners, grill/bumper, and factory headlight assemblies per these instructions.

2.  You should notice that the factory HID system connectors are the same for your new halogen headlight assemblies.  This was a relief!  It just plugs in and if you are converting to halogens, then you're done.  

3.  Plug in the connectors and test your new headlight assemblies with the HID's installed.  Mine didn't work.  With a test light I figured out that I needed to flip the connector that goes into the HID ballast to get it to work.  Luckily, it will plug in backwards with some help.   Again, I had to reverse the plug into the ballast (blue wire and black wire).

4.  Find a place to mount the ballasts.  This took a long time for me and I actually mounted them twice before finding a suitable location.  You should skip straight to what I ended up doing.  The aftermarket halogen assemblies have a place to bolt in a factory ballast just like your originals.  This locations wouldn't fit my new ballasts, so I ended up grinding away the plastic until it would fit.  I used some plumbers strap and a couple screws into the factory ballast location to hold it in place.  I'm fairly confident that this is the only place you can mount the ballast, if they are like mine were.

5.  Drill a hole in the back of the headlight assembly to pass the wires through.  This will become obvious.   You will need a hole saw matched to the grommet provided in the HID kit.  Mine called for 21mm, which I found later was a misprint.  I ended up using a 1-1/8" (29mm) hole saw.

6.  Put it all back together using your instructions.

In all, this took me about 5 hours, but if I'd had some instructions like these it could have been 3 hours.

Note:  Mine had the headlight washers system.  I pulled the hoses from this system and plugged the remaining hose with a bolt and clamp.  I zip tied the remaining hose to the power steering cooler to keep it from causing trouble.

Update:  I ebay'd my OEM ballasts and bulbs for $199 in an hour to a guy who is going to re-sell them.  And my sun damaged assemblies for $115.  This can be a cheap modification!