MA666

Hi,Hopefully some one can help , I have searched the internet and had the car in the garage but no luck. Being able to find a solution would mean a lot , as I can not afford to or don’t want to scrap the car.
It’s is a Vectra c , 54 plate 1.8 unleaded. A few years ago the I the water in the foot well issue, the the heater started to play up , replaced the resister a few times, the replaced the fan motor about a year ago - it’s not starting to play up , will work sometime and does not work at all at others - any thoughts on what to check next , even if the fix is a stop gap I can live with , any advice help appreciate, happy to supply more details. Thanks in anticipation