2 issues with tankless water heater. Flow rate and temp is the key.

1) Shower electric heater - one normally requires hefty cables if the water demand is high. May run off 2 phases 110V.

2) Gas heater - better than electric. In the past, the 'tank' does not last long as it may be constantly firing. It may have been improved in recent years.

Need above average DIY skills to install either one.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.