I have a 1941 Oldsmobile and when I hit the headlight dimmer switch to select high beams my headlights cut out My car has all original wiring and I suspect a short at one of the terminal blocks. I am unsure how to troubleshoot this problem Any suggestions? I cannot select my model number below I have a model 76 Dynamic Cruiser.
I think I’d start with the floor switch which was prone to damage. Or take it out and have a good look at it and test the terminals. Do you have a Chiltons or something with the wiring diagram. It should be fairly simple. Must be a separate circuit for the highs. If it was a short, I would think it’d be blowing the fuse. I’d take the switch out then connect a 6V power supply like a battery charger to the wire going to the highs and to ground to see if they work then.
+1 to Bing’s suggestion. Can you use a multimeter?
Yes, time to get out the volt/ohmmeter. This is a required tool, especially for a car this age. Keeping all the wiring and connections in good shape is a key to living with an old car, a 6V car in particular. Figure out which wires are in the circuit, which switches, and which connections, and check them all out.
We also need to see some pictures.
If you had “a short”, fuses would blow or something would start to burn. Sounds more like the floor switch is tired or corroded and needs replacement. I had to replace the floor switch on the first car I had for exactly the same symptoms. You can remove the wires from the switch and check continuity with an ohmmeter. Sometimes I wish cars still had the hi/lo beam switch on the floor.
Check out Rock Auto, they have this for just $27:
They have a dimmer switch, too.
Wow. Order the switch and the book at the same time and save postage. Get on their email list and get a monthly newsletter that is interesting. Fine folks.
Also, look for bad/corroded grounding around the headlights and headlight sockets.
For the hi beam headlights to work the power has to go – assuming a negative ground system – on a complete low-resistance path from the battery positive terminal, through a fuse or circuit breaker, through the headlight switch, through the lo/hi beam switch, to the bulb socket (filament pin), to the bulb filament, to the bulb socket (ground), to the chassis ground, then back to the battery negative terminal.
Somewhere along the line that path is broken or has developed a high resistance. One approach is to start with the easiest stuff to test first; e.g. the fuse, battery cable terminals, bulb-to-bulb-socket, connection from bulb socket to chassis ground. Another approach is to make an educated guess; e.g. it only affects the high beams, so it is either the high beam fuse or the hi/lo selector switch, so I’ll test those first. Another approach is to turn the hi beams on, then (assuming they don’t light) simply start at the beginning of the path, at the battery, and trace each intermediate point using a DVM measuring the volt reading, step by step until you find out where the voltage is not making it through.
And just make SURE it’s not the bulbs.
I have changed the dimmer switch and I still have the problem. The instrument lights also go out when the high beams are selected but the tail lights remain lit. I have the original shop manual for my car as well. I have some photos of
Sounds like you might have a bad/loose/broken connection or wire (or maybe the main light switch) somewhere. You’ll need to take a voltmeter and start measuring.
I’ve always liked the styling of those 1940’s cars. That’s a nice restore you have there OP!
The photo remind me when my family had an old 1940’s Packard that looked sort of like that, and every time that car went uphill it would backfire like crazy. I mean really loud backfires, and lots of them. What with the backfiring and the FBI look, I thought that was the coolest car on the road! … lol …
I don’t have a schematic for this car but guessing a bit I tend to agree with texases about the main lighting switch.
Nice, nice car by the way. I’m a sucker for cars that are out of the norm. There’s 55 Chevys and 30s era Fords all over the place so a '41 Olds falls into the supercool range due to rarity.
I was very close to buying a '48 Olds many years ago but passed on it at the last minute. However, it wasn’t original. It had gold flake paint and a 350 Chevy with dual 4 barrel carbs.
The paint sparkled in the sun but I just couldn’t get past the paint color issue.
I have an NOS light switch but haven’t tried to put it in yet.
Here is another picture of my 41
Looks superb from that angle too! 
I wish car designers would go back to the half moon hubcap look like that, and away from the wagon wheel look.
Here is another picture. Taken with my phone.