From Michael Hutton
Attach a thermocouple to the bulb and leave the meter outside the fridge; on
most of these devices the leads are thin enough for you to be able to close the
door on them. If you don’t get a steady rise in temperature, the light is
off.
If you have a camera with a timed shutter release, leave that inside and see
whether the film is fogged when you develop it.
London
