The failure of the resistor pack seems a common problem but it's easily fixed. On the card (which is located next to the heater motor, behind the glove box, held in place with two screws) you will find two raised lumps sometimes under a metal cover, these appear to be a type of thermal link but the connection breaks after a while, the trick is to clean them off and solder across gap. I did this on mine two years ago and its been fine since.I also done a neighbours last winter and his is still fine.
Trevor Smith
1600 Primera P10