Hello all-
My daughters '89 740 sedan, b230f non turbo, has a very intermittent starting issue. In the process of debugging it, I came across something that I can't figure out. When I was tracing what wire did what at the interlock switch, I found a blue/green wire at the connector for the interlock switch which is the same color as the wire at the starter solenoid. I thought, "Ah Hah!". When I disconnected the wire from the starter and switch connector and checked for continuity, I got continuity. Woo hoo. However, when I checked for voltage with the ignition at position II, at the switch connector end, I got none. But at the starter end, I got 12 volts. Boo hoo. This really puzzled me because this wire is what energizes the coil to make the starter engage and spin. I then connected the starter end back onto the starter and checked the voltage there. It was in the millivolts range (essentially zero). It appears that this is a phantom voltage of some sort (so little current that it shows 12V with no load but 0V with a load). The only thing I can think of is that there is a relay or something in-between the switch's connector and the starter. Perhaps the output from the relay is also connected to the coil? Solid state circuits do this sometimes too. A starter relay would seem reasonable because the interlock switch's contacts are kind of light to be able to take the current required to engage the solenoid. Whatever this device is, it may be what is at fault because everything else has checked out fine.

I checked the FAQ's (they are awesome), but couldn't find any description of any sort of device and the engine electrical diagram from the autoelectric website doesn't show anything. You guys have saved my bacon several times in the past, your help this time would be once again, greatly appreciated.
Thanks
Dave
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'97 110K+miles 850 grey wagon, '91 300K+ dark grey 740 wagon (130K driven since purchased & has thankfully quit only once), '89 200K+ grey 740 sedan (gave as gift to daughter)