I know the issue and the recall well .. i can actually say we did the recall and then there was a recall again on the parts we had fitted as they changed the design of the valves yet again !
Although one of them did give a coolant message on the dash due to a thermostate valve failure none of the valves have much to do with the heater blowing cold air ..
Well as far as im aware anyways .... i never really checked it ..
In fact the only message was about coolant / thermostate when in fact 8 valves had actually stopped working .. car cant monitor them .. 8 things inop and 1 message
Basically though you will get a coolant failure message if its the valves displayed on the dash.
Im not sure what tester you have or if it will be able to go into the A/C system .. try it though .. if you can find A/C on the list of modules have a look .. if you can get at fault codes for that system it would help.
Intermitant fault .. hmm .. strikes me it is temp related so more likely to be a sticking flap motor perhaps .
Im guessing though .. always a bad idea
Monitor it and see how it goes and let me know if you can get a code.