My brake lights are driving me nuts. Basically, all combinations of the rear lights on my 67 work EXCEPT brake lights & turn signals together.
-Individually (turn, brake, tails), they're fine.
-Brake lights and taillights together are fine.
-Taillights and Turn lights together are fine.
But when the turn signals and brake lights are on together, only the signalled side works (flashes). The other side (the brakje side - that should be on constant) is dark. My grounds *seem* fine, hazards work fine, no dimming or signs of bad grounds. What am I missing??
Driving in traffic and choosing between signalling and braking have been my options, but I can't keep it up for too long
A lot of the old shop manuals say to disconnect the original switch and just plug-in a new turn signal switch and see if the problem is fixed. That was easy when switches were a dime a dozen. If you are lucky enough to have access to a spare 1967-68 switch, that is the easiest approach.
BTW, don't ever spray WD40 on electrical contacts or components. Use specific electrical contact sprays.
I had a similar problem. It sounds like your turn signal switch is broken and is traveling too far. One way to check this is to turn on the turn signal but make sure that you only move it just enough to turn it on.
There are little tabs/stops on the turn signal and they can break off. If they break off, the switch travels too far and doesn't work correctly. The switch is about $50 at the parts store but I got mine on ebay for $24 + $5 shipping.
I had the same happen to my car, it was just as camarorsconv said. The little stop tabs break off and the switch over-travels. The tabs are about 1/8" square and you'll probably find them laying in the bottom of the column housing of the switch area.
I fixed mine by using RTV and basically making new stops. Just cleaned the area and put a small blob in place. Then of course a month later the other tab broke off and I got to take the steering wheel off again. But was better at it the second time around.