With the cold weather getting terrible condensation particularly inside the rear window ..so bad its dripping onto the rear shelf. So I bought from Amazon a £27 ..$40 de humidifier . First 12 hr test nothing in the water vessel. Examination showed the cooling element was solid with ice but it had been over cooled so nothing in the water vessel.
Solution under test at present was a mains timer 3hrs on and 1 hr off to allow the ice to melt. We will see if I send it back but the makers must know of this problem and should have the cooling element just above freezing or build in a de frost mechanism.
For those who dont know its a piezoelectric element that cools the incoming air causing condensation on the cooling element ..well ice in this case so no run off to the holding tank

 

I'm hoping to avoid this and have a sock full of cat litter to act as a minimal desiccant.

With the XJ6 which did suffer I realised running the air con all the time helped a lot.

 

I have changed the timer settings to 3/4 hr ON and 1/4 OFF as I realized that when you switch off the heat from the hot side of the piezo will conduct across and melt the ice on the cool side then water goes into the holding tank.

 

I'll be interested to shear how effective this.

 

I have it on the 45/15 ON/OFF and it seems to drop the ice when off and the tank fills up. You cannot expect vast quantities of water every day as its only a small volume but I like the idea of any damp in the car being extracted .
Must get a hygrometer to check the true status.
This is the one I got ..the first did not arrive and I paid £27 as I got a used one which turned out to be new.

 

Had some conversations with the makers ... they say not suitable for a car as you don't have mains supply !!! They also say it only works between 15c and 35 c .I guess below 15c it just ices up . However with my 45min/15min On/OFF cycle it works whatever the temperature and is pulling about 100ml of water out per day . No idea where its coming from as its not wet or damp inside ...anyway must be a good idea so I am going to use it in the winter period.

 

I have used a dehumidifier in a damp flat and 100ml a day is nothing, I could get 500 ml in a couple of hours but it was pretty damp in a Welsh way. I suspect your regime will be very successful.