When I turn on the heating for the saloon, it is ok, but when turning on heating for the front and defrost, the car almost gets turned off. I feel like the electricity is going down. What can be the matter ?
This sounds like a voltage drop. The most likely candidates are:
- the heater resistor
- the heater fan
These components are usually located right next to eachother, in the footwell if the front passenger. The resistor can be electrically tested using a multi-meter (measure the resistance through all combinations of connections), the fan too.
Also check that the fan can spin easily and freely by hand, sometimes the fan is electrically fine, it's just mechanically binding.
For most cars, the resistor should be inexpensive, the fan should cost a bit more.