BenzWorld Senior Member
Date registered: Jan 2009
Vehicle: 1980 450SL named Freya. 202,000mi
Location: Hollywood, Ca.
Mentioned: 3 Post(s)
Quoted: 142 Post(s)
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Pin (updated Nov. 26 to correctly reflect the 1980 thru 1985 versions of this vehucle).
1 RPM signal, 0 to 12 V, 4 pulses per revolution. A frequency of 43.3 pulses per second corresponds to the desired idle speed of 650 RPM. (To check your tachometer you could measure the frequency at this pin and multiply by 15 to get RPM.) This signal is derived from the ignition amplifier and is synchronized with the low side of the ignition coil.
3 Frequency Valve signal. This is a tap of the signal that drives the frequency valve. This signal can NOT be read with a duty cycle meter. You need either the Bosch tool, OR an oscilloscope to read the signal on pin 3.
4 Low (negative) side of the ignition coil. This is where to monitor the dwell angle of the electronic ignition amplifier, and is also a good place to view a reflected and attenuated image of the spark. This is about 50 VPP, safe for an ordinary oscilloscope.
5 Hot (battery voltage) in Run or Start, NOT FUSED! This is actually the positive side of the ignition coil.
6 Hot at all times, through fuse 2
7 Shielded cable from TDC sensor. This is not the same sensor which triggers the spark control unit, but it could be used in a clever circuit with pin 1 to measure spark advance.
8 Shielded cable from TDC sensor.
9 Shield for pins 7 and 8.
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