s40 (2001) heater works intermittently

i have a 2001 volvo s40 with air conditioning sometimes the blower works and
sometimes it works for a short time but not long enough to get the car warm
this condition exists either with air conditioning on or off
i bought a haynes manual but it doesnt help really
i have a feeling a sensor has gone down somewhere and is reporting a false
temperature but dont know where to start and cant afford a volvo dealership
at the mo

i would appreciate anyones help on this as winter is nigh
Thanks again

 

Is it just the blower coming and going? It could be as simple as a loose
connection, could be a bad blower motor. I would start by making sure
the fuse is fully inserted, then locate the blower motor and check for
voltage. I'm guessing there must be a mode that bypasses any sort of
climate control and just turns the fan on?