I had a similar problem. The fan would never come on until the gauge got to the L. I took it to the dealer time and time again. They finally gave me the same story "it's supposed to do that". Well, it wasn't, and they were wrong. The resistor that goes to the low-speed fan was burned out. So, when the fan finally did come on, it was the high speed fan, which is supposed to only come on if the low-speed fan doesn't do it's job. Just because someone is a mechanic doesn't necessarily mean that he's right.
