This was around a change-over year. I believe this is the 140 chassis, like the chassis they stopped making a couple years ago, correct? If so, on the gas cars, I have heard of this problem. Now, I am unsure about the Diesels, but the gas cars have what is called a "Base Module" On the gas cars, it is located in a box on the passengers side under the hood, towards the back of the engine compartment. If it is there, it is in a box that has a lid fastened down by screws. Take the screws off and open the lid, there are control modules in the box. The one you are looking for has some fuses on the top of it, probably under a clear plastic lid. Open the lid and check those fuses, I'm willing to bet it has a blown fuse in there. I don't thik it would affect the A/C, but if this is an early 140 chassis, they are known to develop leaks in the evaporator core, which is expensive to fix. What is the complaint on the A/C, there are several problems I know about.....Gilly