Hi Shirley,
I assume from your description that the heater does not 'blow' any air into the car but that the car water heats up normally (on the dashboard engine-temperature gauge). This means its an electrical fault with either the heater motor or the wiring. It would be unusual for the wiring to be at fault unless you've recently had something fitted to the dashboard of the car to disturb the wiring. Assuming that you haven't, my best guess is that the motor has failed. This is usually the 'brushes' in the motor rather than the copper 'windings'. Either way, it means the heater motor has to be removed to replace it or just the brushes. Not knowing the actual vehicle, it is not possible for me to say how to go about this, but I think you'll need to take it to a garage as although the fault itself may be easy to fix, getting at the heater motor can be very difficult.
Sorry I can't be of more help but at least you know what it's likely to be and what I would consider to be the best remedy in the absence of knowing the details.
Barry, November 2010
