Yes, the first thing to try is the dimmer switch. Try changing it back and forth from low to high a number of times in succession. Sometimes you'll get it to work intermittently when you do that and then you know that is the issue. If that doesn't change things, then try a test light on the dimmer switch terminals. Chances are good the terminals on it are corroded and also sometimes the terminals in the harness connector are corroded.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
Check the firewall connector, while there check both firewall connectors. If original, be gentle with the plastic.
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63 Parisienne sport coupe (The Big GTO), black, maroon interior, 409 4 speed; former owner of a 59 El Camino, 63 Corvette SWC, 62 Chev Bel Air SC. 1963- Pontiac top selling car in Canada
Mahone Bay, NS Still not old enough to need an automatic