If you have a 240D with EGR like I do, it is very easy to retrofit it with a tach/clock from a 300D turbo. Mine is an 83 240D w a 4 spd manual. I feel it needs a tach more than my 300D automatic so I borrowed the tach/clock from it till I can find another one. I tested the tach with the EGR controller on the floor of 240D on Sat to make sure everything works and installed it on Sun. It's working great! I thought some of you 240D lovers may like to add a tach also thus this DIY. If anything in this DIY is unclear just ask.

You will need to get a working tach/clock from a 300D cluster (not the entire cluster!)

1. Remove passenger side-kick panel and remove the EGR controller mounting hardware (3 bolts).
2. Remove the 4 small screws that secure the EGR controller cover and pull out the board.
3. With a DVM set on AC scale, probe the 2 points where the red and black wires are soldered to the board while engine is running (see pic below). Be careful you don't short anything out! At idle you should have around 0.2 volt. Reving the engine should increase the voltage to near 1.0 volt. If you have voltage there, then your EGR controller will work as a tach amp and drive the tach. All that remains is to feed the signal from the EGR controller to the tach and supply power to it.

Attached Thumbnails

 

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked