I just finished fixing my left headlight assy on my SC400. The culprit on my light assy was the bottom curved drain hose tube was too loose. For some reason the mfg. made them too small and wouldn't stop water flow from the outside of the rubber where it connects to the headlight assy. And my light assy is only a year old. I simply used silicon sealer on it. You have to remove the headlight assy in order to fix it. Taking it off of the car with althe bulb assy's installed gave me a chance to pour water over it from the kitchen spray hose and find the leak. First I had to remove all of the bulb assy's and use a hair dryer untill the the inside was dry. I then used the kitchen spray hose under very low drizzle from one corner of the light assy to the other corner while looking through the clear plastic untill I saw what area the water was leaking from. That should help you out. Taking the headlight assy out of the car is no big deal. You need to jack up that side of the car to gain access to the fender well panel and remove as many screws as needed to pull the panel back enough to gain access to the two mounting nuts located inside the fender well. Then remove the mounting nut from under the hood, disconnect the buld connectors and wiggle the light assy out of the body. Good luck. This worked for me. Ric :)