A couple folks at WCR mentioned loosing their horn after tinkering with the steering column, switches and or knee pad. After my trials and tribulations with the wiring on Mark's car last week. I thought I'd share some insight.

The horn wire carry's thru on the turn signal switch harness. It's the brown white wire on the left side of the connector. Make sure the wire is completely seated into the connector. It popped out 3 or 4 times in my work on Mark's car. Popped out again Friday night when I was working on the ignition switch at WCR.
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Went to the AA website to see if the plastic connector was available. To my surprise it came up as an available item. Probably a good item to replace while your in there. A lot of heat runs thru those connectors. What I was seeing was the sockets for the wire connectors had enlarged a smidgen so that the connector could roll a bit then the pin on the switch would push out the connector.
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Excellent tip. Now If I can just remember this when it happens to me!

A wire connection should grip the pin. The plastic housing shouldn't be doing any work. Replacing it won't solve the problem, or at best will be a band-aid.

If it's popping off, that receptacle (AKA female) is worn. You should pull the receptacle out of the plastic, replace it and then pop it back in.

There is a service life for connect/disconnect cycles. Age and vibration are also factors.

Mark do you have a preferred supplier for the female spade connectors?