Morris, The preheater would not be able to hold the oven at temp. The internal oven must be working or you would not be able to lock. Put the meter position to osc. oven, note reading, unplug unit for about one minute and then plug back in. The meter reading should peg or at least be noticably higher for a a short while than drop back to the initial reading. If that works the approx. 45 reading is where yours runs. There is a select by test resistor on the mainframe to make this read a specific value but does not really do anything else for you! Corby Dawson ____________________________________________________________ Learn to trade with confidence! Online Stock Trading. Click Now! http://thirdpartyoffers.juno.com/TGL2141/fc/Ioyw6i3mKCaQcdhLufhnlHl2nj0ievyXDrgWFbJz5RRpJpU6s4ZqXv/