Do you have instruction for the non contact IR gun? it is very accurate on non shiny surface. Test it with a pan of boiling water to make sure it is correct then point it to the location of the temp sensor or cyl block. If the surface is shiny then tape a 'duct tape' on top and wait for while ( say 5 min ) and redo it again.

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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.