I recently had my 945 fail VA state inspection for a non-functional horn. After testing the horns themselves and confirming they functioned, I then dug out the multimeter and started checking the wiring. COnfirmed 12.5V on the yellow wire at the horn connectors. Then I disconnected the battery to disable the SRS since I expected to be screwing with the steering wheel.

Then I checked for continuity between the blue/black wire (switched ground) and chassis ground--there was NO continuity when the horn button was depressed (none when it wasn't depressed, either, but that's NORMAL). So, that confirmed a problem on the switched ground side of the wiring. First I confirmed the un-switched side of the switches had continuity to ground, then checked the switched sides with the switches depressed. OK. So the problem was between switches and horn connectors. Joy. Based on the wiring diagram, I went in search of C2, a big black 52-connector plug which turns out to live inside the car, tucked way up under the dashboard along the inside of the fender. Found continuity between horn connectors and both sides of the plug, but NO continuity between the switched-side of the switches and the plug. So, the fault was between the switches and the connector. Removed the small access panel on top of the steering column, and discovered the slip ring contact was readily accessible. Confirmed continuity between switches and body side of slip ring, but none between slip ring and C2.

Turns out: there is a spade connector on the back of the assembly where the blue-black wire attaches to the slip ring. This connector had come loose (doubtless when I was removing and reinstalling the instrument cluster last week) creating the open circuit. SO, although the FAQ warns of melting horn switches and common sense warns of badly corroded connections at the horns, if your horn abruptly stops functioning--especially after you've done ANYTHING up inside the dashboard--get out a screwdriver and check the tightness of this simple connector. Because of its location it it highly vulnerable to being yanked loose.

john
--
1989 245 244K / 1993 945 129K