I am not sure on his Model. On mine you only need to insert the Tool/Wire into one hole.

About 2 or 3 weeks ago someone posted a later model Mercedes and on that one you need to insert the Tool into 2 Holes.
I have that particular 2 end Tool that I got when I bought a Lot of Mercedes Tools on Ebay. It is a thick U shaped bent wire with kind of hypodermic needle poits gorund on the ends.
But, that same Tool would not work on mine unless I cut it so I only had one Wire.

I am not sure which one He needs but if he has 2 Notches in His Tumbler Face it is He would likely need to stick something down both Holes when they line up.

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84 300D, 82 Volvo 244Gl Diesel