I simply changed out my HVAC controller light while I had it apart. It's not easy to get to otherwise. The books call for a #74 bulb to replace the factory bulb and it turns out to be just a slight bit larger. This isn't a problem for fitment into the socket BUT the little green condom that goes over the top hardly fits over the larger one. Mine split when I was trying to get it down all the way but it still stayed on. I would throw in some dirty joke but I'm too tired right now.