I have seen many questions here related to blower motor resistors. That sounds like a really old-fashioned kind of technology. This made me wonder whether there are any cars that would use a switched mode power supply (SMPS).

The SMPS would solve several issues. Firstly, you don't need a beefy resistor anymore, so possibly some cost could be saved (integrated circuits are cheap nowadays, and power resistors may be expensive depending on the supported power dissipated). Also, it would reduce heat production and save some energy. Furthermore, an SMPS can support more speed settings than a resistor, and perhaps even a continuous adjustment.

So, do any cars use an SMPS to control the blower motor? Do the new kinds of automatic HVAC systems still use an old-fashioned resistor or an SMPS?

  • My truck which has auto HVAC doesn't use a resistor. I don't know if it's SMPS, but surely could be. Jul 9 '17 at 18:47
  • @Paulster2 I guess it's probably SMPS, as nobody really uses linear regulators these days unless very noise-free power source is required.
    – juhist
    Jul 9 '17 at 18:58
  • I suppose they are using pulse width modulation
    – Martin
    Jul 9 '17 at 21:12
  • I don't see the heat produced by the resistors as a problem - it's part of a heater and there is lots of moving air to cool them... Also, cost is a major issue saving cents per car on 500000 cars is profitable.......
    – Solar Mike
    Jul 9 '17 at 22:08
  • It may be old technology but so is the wheel and we still use that.
    – GdD
    Jul 10 '17 at 8:09

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