Drayton Digistat RF601 thermostat shows incorrectly high temp?

Hi,

A battery leaked in my Drayton Digistat RF601 thermostat so I removed as much of the (small amount) of battery fluid as I could by cleaning the circuit board (batteries out) with kitchen roll and used a hair-drier to dry up any residue.

Now, when the unit is switched on it shoes an error code "30.4" after which it shows the usual display but with a much higher temp reading than the ambient temp arount the unit. That is, the temp indicated differs between 29 and 31 degrees c while the ambient temp around the unit is more like 18 degrees c.

The unit seems to operate Ok, in that I can set a temp by the rotary control, but I don't know if the unit actually triggers the boiler as I can't set the dial high enough!

Any ideas please????

This is my second unit in as many years, so I'm hoping I don't have to buy a new thermostat (the receiver is fine), at an extortionate cost!

Many thanks,

Bob