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I'm in the process of installing a Momo Model 78 wheel on my 968 track car, and the link to Dave Greimann's procedure (I sure miss Dave - one of the smartest guys to have ever owned a 968, for sure) has been very helpful. I've installed the wiper connector (part number 928-652-104-00), have placed a 3 ohm resist across the appropriate connector leads, and identified the wire that's got +12V when the key is on, which should constitute the "hot" lead to the horn button. Here's how it looks:
The other connector on the back of the horn button should go to ground, which should be established via the wire coming from the hub adapter which is attached to the conductive strip on the back of the adapter, which pushes against the wiper connector shown in the picture above, which should be grounded. Here's a picture of the wiper connector next to the hub adapter, which shows everything I'm describing:
Just one problem: when I place my voltmeter between the hot wire and the wiper connector with the key in the on position, I get no reading. The wiper connector is not connected to ground, in other words. When I touch the ground lead on my voltmeter against the steering shaft, or any other chassis ground, I get a solid 12+ volts. Any ideas what to check or try next? I've never been an avid horn user, so I can't say with certainty whether the horn ever worked correctly with the stock wheel, but it seems strange for ground to have disappeared as the failure mechanism, so it seems like I must be missing something. Thanks.
OK, I've figure it out - it turns out the hole that the wiper connector goes into is actually also connected to a source of +12V with the key on. I had assumed it was, or should be, connected to ground, because that brown/white wire that was connected to the stock clock spring is connected to +12V, as stated above. So I need to use the wire on my hub adapter that's connected to the brass ring on its back that makes contact with the wiper connector as the hot lead for the horn button, and find a source of ground for its other connector. The body of the hub adapter, which is connected to the grounded steering shaft, should do the trick.
07-21-2010, 12:27 AM
