Recently the ballast on my IS 350 went out. The only fix is a) get a used ballast or b) get the whole headlight assembly from Lexus. Last I checked Lexus did not sell just the ballast themselves, Lexus's fix is to change the whole assembly. I didn't really want to pay the exuberant cost of getting a whole new headlight just for the ballast so went ahead and tried changing the HID’s from a D4 to a D2 bulb and retrofit an aftermarket ballast. Excuse the quality of the pics, camera phone pics.
First step take headlight out:
This image shows the wiring on the stock headlight. Getting the ballast off is pretty self explanatory. Get the brackets on top of the ballast off and remove the 4 screws for the ballast.
The ballast shows two sets of wires the blue and dark grey wires are power for the ballast and under the mesh braid looking protector are red and white wires which power the bulb.
I used 9006 style connectors male and female to complete my connections. You can use whatever I just had these.
You will see the rubber grommet where the blue and dark grey wire goes to power the ballast. Cut these and I connected these to a 9006 male connector blue to red and dark grey to black.
Reroute the red and white wire that power the bulb out of the housing by drilling two holes enough for the wires to slide out from inside the housing. I connected those to a female end of a 9006 style connector. Red to red and white to black.
On the after market ballast I cut the ends of the wire that is used to power the bulb and replaced the connectors with a male 9006 style connector. Red to red and black to black.
Now reassemble the headlight. I put the stock ballast in its original position to seal it back up properly, I used some RTV around the holes that were made to reroute wires out of the housing. Everything was soldered and heat shrink was used on all the joints and just for added security used electric tape to go over all the joints.
Don’t have any pics of the complete assembly with the ballast but I just zip tied the ballast to the bottom of the headlight housing enough to where it was pretty secure there.
Of course change the bulb out, D4 to D2. Put your headlight back, connect your wiring harness and you are good to go.