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Hi all. I’ve just removed the speedometer from my ’92 940T, using the excellent description from the FAQs, to fix the infamous capacitor problem. The FAQs described how the speedo could be tested in the car by disconnecting the connectors in the trunk and that rapidly shorting the two wires together that go to the speedo from the speed sensor would simulate the pulses it generates and cause the speedo to register speed. Now that I have both the cluster and the speedo out, it seems that it would be really easy to test the instrument by doing the same test on my desk. The 4 pin connector on the cluster is marked as “+” “-“ “S-“ and “S+”. The four main connections to the unit, through the four screws, are marked “IGN”, “48P”, “SRL” and “GND”. The fifth connection is marked “E - PULSE” and connects directly to “S+” (probably the output to the ODO circuit). There is also a two pin spade connector marked “12P” that has a separate plug going to it. One of the wires in this plug is red which, along with the “12P” would suggest that 12 volts should go to it, but I don’t want to test this theory unless I know that for sure. Anybody know what this plug is for? The “IGN” connection on the speedo would suggest that 12 volts should be sent to it as well to simulate a turned-on ignition switch. I don’t know what the “48P” and “SRL” would mean. Has anybody ever tested the speedo on their bench by connecting 12 volts to the “+” and “-“ connections and rapidly connecting the “S-“ and “S+” together on the speedo, possibly connecting 12 volts to the “IGN” and “GND” at the screws as well? Thanks.
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