I went out to take a run in my 66 122s, and before Ii pulled out of the yard I did my usual Safety Check, only to find that My Brake Lites & Horn don't work.
I just so happened to have a new Brake Light Switch #672425, and installed it.
I topped of the Brake Fluid, and tested the Brake lites again, and there still not functioning.
I checked the Bulbs, Wires, and ran a continuvity check...no electrical signal
to the brake lites. The Driving Lites work, Sigles work, and Reverse Lites luminate.......VERY CONFUSING !!!
Also, the Horn is not functioning.......maybe it was a rodent, or am I a victim of The Swedish Electrical Gnome

Any ideas???
Thaks
PTRABS

Paul;

Brake Lights and Horn are on the same (Fuse 2) circuit, so you should check fuse and its connections first....especially in Rhode Island where ocean air may have accelerated growth of oxidation and the resulting poor connections. Any functional tests on this circuit will need to be performed with IGN ON.

66 122 had a hydraulic Brakelight Switch with the well known and documented reliability issues (see: http://www.sw-em.com/safety_bulletin_4.htm )...after locating and repairing Brakelight issue, you may want to consider upgrading to the MUCH more reliable Pedal Position Sensing Switch...and apply ACZP to all electrical connections involved while you're at it.

The Horns themselves are also a weak area, because of how rarely the get used and their position in from of the radiator where they area optimally placed for corrosion attack...not to mention the weakness of the hornring switch and no relay...again, (only AFTER trouble is located and repaired) do I recommend considering an upgrade to add a relay...see: http://www.sw-em.com/122_horn_notes.htm

Cheers from Connecticut!

you need to slow down when diagnosing. a quick google of 120 wiring diagram shows that one fuse supplies the brake lights, horn and the reverse lights...chances are the fuse contacts need cleaning or (less likely) the fuse is blown. Fuse box PM is the number one area for electrical reliability.
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Patrick, '68 220 (used to drive 240s) '53 GMC 4104

and I need to read more carefully! in the diagram reverse is on the same fuse, so your post that the reverse lights work belies my conclusion. I will however posit the you may have a different set up (PO mcgiver or manufacturing change) whenever 2 electrical systems fail at the same time 1st place to look is the FB.
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Patrick, '68 220 (used to drive 240s) '53 GMC 4104

First, connect the two wires that go to the switch together. That effectively bypasses the switch and the lights should be on all the time.

If they don't come on, you have a problem before the switch... check fuses, grounds at the back, and of course bulbs.

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-Matt I ♥ my ♂