Phil, according to the wiring diagram in the green books, power is fed via the horn relay #85 pin to the "relay for signaling" that appears to control the fog lights - so there's some connection between the two, at least, though I don't understand why Volvo chose to do it this way or what difference it makes to the operation of the horn and fog lamps. My guess, though, is that there's supposed to be some connection - otherwise why call it the "relay for signaling?"

The biggest puzzle for me at the moment is the main fog lamp relay (#9 in the green book diagram). When the fog lamp switch is activated and the headlights are on, the relay is connected to +12v at both ends of the control circuit - pin 85 on the relay is connected to pin 58 on the light switch, and pin 86 on the relay is connected via the power circuit on the signaling relay (#11) to pin 56 on the light switch). This should, in theory, result in no current flow and no operation of the relay - exactly the opposite of the desired result, which would be to feed power to the fog lamps.

So what am I missing here? There's clearly some reason why the Volvo engineers created such an elaborate setup for the 123GT, but I can't figure out what it is. If all they'd wanted was to have relays control the hron and fog lights, they could have eliminated the #11 relay altogether. Any theories?

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The other Phil S. | '68 Amazon daily driver