I have reinstalled my harmony stereo

[baconbuttyman]

For as long as I can remember now, when I turn on the rear window down demister, the reception on my Dynavin DVD satnav system deteriorated badly, so this week I uninstalled it all, disconnected the power etc and reinstalled the OEM stereo, low and behold the reception still degrades when the rear heater is on, I know this is the aerial too, but, I have run a separate live to the antenna module already, so i know it's not that, I am thinking perhaps there is an issue with my climate control unit, aim to rewire the whole stereo system in a bid to cure it