As a guess only,
I would thinks a general cleaning the dust buildup off all
Components & wiring/connection checks
Cheers
My RF60's now just over 10 years old and that's all I've ever done myself. Every year or 2, 4 screws to undo the the cover and clean out the insides with an air blower. There's not much to an Evakool, so if it's working, other than cleaning I'm not sure what they'd do in a service?
Hasn't all been roses with my Evakool. About 3 years ago it stopped working while camping. About 15 minutes of testing with a multimeter and I worked out it was the mechanical thermostat. It doesn't appear to be a serviceable part, but with a bit of patience you can carefully pry apart the thermostat housing and clean the contacts with a points file. Works a treat and haven't touched it since.