my humidex dehumidifier is icing up at the back?

I have same problem with an old metal cased Humidex 4 - there is a timer PCB and a relay to operate the defrost valve which has failed so it never defrosts (check it every 10 mins to see). I now use a plug in timer set to go off for 15mins every hour. This unit though rusty and decrepit is SO MUCH BETTER than a new one I bought which uses more power, is much noisier and takes out LESS water per 24Hrs - so well worth keeping it going !

Geoffa
January 2011