Heater question

[Xaccers]

Water always flows through the matrix.
The heat control just directs air across it for heat.

[CitroJim]

Yes, but and just a small but. They can leak a little through summer and due to the design of the heater box and flaps you'll not smell it as all air is well diverted around the matrix. As soon as you slide toward the warm end of the dial the air will pass through the matrix and you may get a whiff of finest curry for a short while...

If the leak is tiny then the curry will waft for mere seconds and then clear never to return until again the slider is pushed over to chilly for a while and then slid back to mildly tropical again...