Sounds like the handle is attached to the dash board. If that is correct, look to see if there is something like a "Cap" on the end of it. If there is a Cap, try twisting it. If it turns, that could very well be your adjuster. Also, if it is, turn it a little then pull up on it, then repeat till you get it just right. Otherwise, check under the truck as your mechanic has suggested.
Bill
