I just changed my headlight switch in a 1974 BC my dimmer didnt work. I also had a spare spade terminal on the new switch. Still worked fine. I imagine it's made that way for multiple year fitment. I'm betting bad ground on the radiator support/ firewall on the harness. Or dimmer switch. Both easy to change/check. I rock auto cheapo stuff like this to just have around as spares... literally got a high beam switch for $2. Headlight switch for maybe $5
