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On 1 Dec 2005 at 9:50, Chris Wright wrote: > I ran a stock 6v wiper setup on 12v for 7 years on my previous car using > an electronic voltage reducer from BugPack or Empi, (I forget which). > This had a speed control knob on it too so when mounted under the dash, > you got useful variable-speed wipers. Voltadrop resistors are no use as > their resistance reduces as they get hot and the wiper speed gets faster > and faster until it overrides the autostop mechanism. But these little > electronic voltage reducers with speed control are really excellent. > They were around £35 in the UK, probably only about $35 in the US. These are probably a decent solution, but I'm bothered by something here that no one ever seems to be aware of: power consumption. Because the 6V wiper works on half voltage, it needs double the current to produce the same power as a 12V motor. If you run one in a 12V system with any of the devices described above, then what the motor still gets is 6V at double current. Now that alone would not be a problem, because that's the same power that the 12V motor draws, but now whatever device you've installed to drop the voltage to your wiper motor also has 6V across it and the same double current thru it, so whatever power is being used by the motor must also be dissipated by the device, and the end result is that you're now using twice the power to run this system, and half of it is just being wasted as heat. Now doubling the power consumption of a small current consumer wouldn't be such a big deal, but the wiper is just about the largest power consumer in your whole car, so this is a big deal. In the end, I'd say that the best solution is what Steve suggested, which was to find a 12V motor from a '67-70 car, or just install the whole system from a '70. From '71 on, everything changed, so I don't think you can use that motor. -- Jim Adney jadney@vwtype3.org Madison, WI 53711-3054 USA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~