Heat exchanger

The heat exchanger (1) has a conductor and/or an electrical resistance heating element i.e. positive temperature coefficient element, arranged in a hollow chamber, which is defined by a hollow chamber wall. An electrical insulating element i.e. form seal, electrically insulates the conductor from a heat conducting element. The conducting element transfers heat from the heating element to liquid to be heated. The insulating element partially fills the hollow chamber. The conductor and/or the electrical resistance heating element is partially electrically insulated from the hollow chamber wall. An independent claim is also included for a method for manufacturing a heat exchanger or a motor vehicle air-conditioning system.