Believer me the lower hose heater gets the block and coolant hot by convection currents just like the factory heater. And the Mercedes source heater is not 1000 watts, but 600 watts just like the one I have.

Check out the pictorial

http://dieselgiant.com/mercedesblockheaterinstall.htm

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1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
Mercedes How-To and Repair Pictorials
I love the smell of diesel smoke in my hair