I had this problem on my BMW, but it may be completely different on your Honda. In my case, my headlights would dim as I was coming off throttle down to idle. I was able to see in the car's computer system that my voltage was jumping all over the place - from 10V at idle to 14.2V at peak. It should be a steady 13.5 to 13.8V all the time. Turned out I had a bad voltage regulator (part of the alternator on the BMW) and some corrosion on the ground junctions. Once this work was done, no more dimming.
The Honda tech should check voltage at the battery, alternator, and at the headlights while this problem is occurring. If he is seeing a voltage drop at one of these locations, he can begin to pinpoint the problem. I haven't turned on the AC, but I'll try it tonight to see if I get any dimming on my '07?
