I'm new here and just picked up a used Jan '07 Lotus Exige S almost two weeks ago. I have this very same problem, and noticed I can only reproduce it when the A/C is on. It must be some devine Lotus providance that this topic was resurected this week when I was thinking of kicking myself for plunging into this purchase for a track car.
Glad to help :-) it looks like an easy swap, but after buying the car, $180 part is not making me smile. I was looking for a good inexpensive source. The labor as described doesn't look that bad