Make sure you don't bend pins when putting in headlight assembly
 

Just a note to everyone that the design of the headlight assembly connector is NOT foolproof. It IS possible to bend a couple of the pins when sliding in the assembly and then (at least for me, when the "outer" set of 2 pins is bent) the main headlight bulb and the turn signal will no longer work. I straightened out the 2 pins and all is well.

I've taken out and put back the headlight assemblies for the 996TT and my previous 986 a number of times and so I am familiar with the process. I was not heavy handed when I did it today. Nevertheless 2 pins were bent.

How did I notice? It was convoluted actually. I had what I thought was a burnt out headlight bulb. When I replaced the bulb I had noticed that a small wire going to the igniter had come loose (came off of the spade connector; it was just friction fit). I thought it might have come loose when I was taking the cover off the assembly. No matter. I reconnected the wire, swapped in a used but known-good-bulb for the one that I thought was defective and was dismayed to find that the known-good-bulb also didn't work. Well, maybe the used bulb was indeed dead. Swapped in another used-but-still-working-previously good bulb. Again, no joy. Started to think it was a bad igniter. Made a note to check to see if I could obtain just the igniter part of the assembly. Started driving the car and noticed the signal light was not working (fast blink). Coincidence? I took off the headlight assembly and tested the signal bulb with a multimeter. Bulb was good. THEN looked at the electrical connector of headlight assembly and saw that 2 of the pins were bent. Straightened them and then both the headlight bulb and turn signal bulb was working again.

Good advice, thanks a lot!

did the exact same thing, turn signal and all. Easy fix though.