to test if any infrared remote control is working there is a very simple test you can do. most of us now days have either cell phone cameras or a digital camera, and theses units can be a useful tool to verify that all types of Ir remotes ranging from your television remote to the remote that unlocks the newer Mercedes cars.
what you do is power on the digital camera and look at the viewfinder, aim the remote at the camera and push all buttons individually, if the unit is working you will see a transmitted light, if you don't see the light from the remote output the unit is bad or the batteries are dead.
not sure why this works, but it does and has helped me many times to determine if a remote is actually functioning or not.

__________________
1967 250 S
1967 280SE
1968 250S
1971 280 SE
1973 220
1974 280 S
1975 450 SEL
1976 220 D
1979 300SD
1983 300 SD
1985 230 TE euro
1986 280SL
1986 500 SEL euro
1986 190E 2.3
1990 300 SE
2003 C230 K
2004 C230 K
1987 560SEL
1987 300SDL now in canada
2005 C230
1998 C43 AMG Sold to DON
1993 190E 2.6
300TD Former daily driver Totaled
current:
R320 CDI
Ram 2500 Cummins