Hi, I have two units with problems. 1. when I power the unit on, the green light comes on, the bulb lights but immediately goes off again. The fan continues to run and after around 10 seconds the light comes on and then immediately back off again. This repeats every 10 seconds or so. 2. The second unit, when I power it on, the light shows red and nothing happens. I have swapped the lamps between units, but that makes no difference. Any ideas?