I just installed my unit into the Saturn last night. Today, went on a rather long drive, and hijack reported the temperature at 58C/136F

But are we sure that it is really running that warm? I mean, how accurate is the sensor? Is it possible that the sensor is reporting a higher temperature than really exists?

58C/136F is hot enough that you would not be able to place your hand flat on something that temperature and hold it there. I wouldn't think the insides would be a lot warmer than the top of the case... My case has only ever gotten too hot to hold my hand on one time, and that was in my bikempeg installation, with the sun shining directly on it for several hours (riding in a parade with the local bicycle club) at very low speeds. I think it got hotter from the sun than it did from the operation of its electronics.

Does anybody have one of those laser gun temperature readers that mechanics use?

tanstaafl.