1940 Roadking lights issue

[Jayden S]

Hello my dad and I recently picked up a 1940 roadking, all original. We can’t seem to figure out the lights. The only lights we can get to turn on are the fog lights. No headlights, tail lights, or high beams. Are we overlooking something?

[Sniper]

Well, since all the non-working lights go thru the head light switch and fuse did you check those?

 

Do the brake lights or turn signals work?

[greg g]

There should be a fuse integral with the light switch.  It's a 30 amp and it's a different length than the common SAE glass tube fuse.  Check that, also if the car has been sitting a while there might be corrosion on the switch terminals.  Running the switch through its travel a dozen cycles can clean the contacts.  Alsohe stomp switch for high beams can also be a point of high resistance cycling it can also clean it's internals.  Also there is a distribution point usually on the radiator support or inner fender where the circuits come out from the switches and divide to each side.  Connections there need to be clean and tight.  Make yourself a six foot long jumper wire 12 gauge with an alligator clip on each end. Use it to power things direct from the battery.  NOTE.  stock this car was equiped as a 6 volt POSITIVE ground system.  So when powering with the jumper wire it gets connected to the negative battery post.

 

Six volt systems are dependant on current flow.  They like thick wires, clean tight connections, good grounds.  If your car doesn't have a ground strap from the body to the frame or engine, install one.  Connect any through bolt on the fire wall to a spot on the engine or frame.  Some folks use one of the bell housing to block bolts.  This will help all the body grounded electrical stuff work better.

 

The primary battery cable from battery to starter should be O gauge wire. Skinny 12 volt stuff doesn't carry enough amps for six volt.

[chrysler1941]

I concur with everything greg g wrote. Just want to add 2 things.

Being a 1940, you may like mine has, a special ground strap stud. This stud is part of one of the 2 bolts that fastens the generator bracket to block.

 

The alligator jumper wire should have a fuse, for example 30A.

[greg g]

And insulated clips...

 

You also need one of these

[chrysler1941]

1 hour ago, greg g said:

And insulated clips...

 

You also need one of these

And change the bulb to 6v ?

[keithb7]

I like participating in electrical discussions but its pretty hard to supplement what’s been said above. Great info. 
 

If you don’t have a digital multi-meter it’ll really be worth the purchase price to fix your issues.  Do you have a shop manual with the electrical layout diagram? Also extremely beneficial to trace wires and electron flow. 

[Jayden S]

6 hours ago, greg g said:

There should be a fuse integral with the light switch.  It's a 30 amp and it's a different length than the common SAE glass tube fuse.  Check that, also if the car has been sitting a while there might be corrosion on the switch terminals.  Running the switch through its travel a dozen cycles can clean the contacts.  Alsohe stomp switch for high beams can also be a point of high resistance cycling it can also clean it's internals.  Also there is a distribution point usually on the radiator support or inner fender where the circuits come out from the switches and divide to each side.  Connections there need to be clean and tight.  Make yourself a six foot long jumper wire 12 gauge with an alligator clip on each end. Use it to power things direct from the battery.  NOTE.  stock this car was equiped as a 6 volt POSITIVE ground system.  So when powering with the jumper wire it gets connected to the negative battery post.

 

Six volt systems are dependant on current flow.  They like thick wires, clean tight connections, good grounds.  If your car doesn't have a ground strap from the body to the frame or engine, install one.  Connect any through bolt on the fire wall to a spot on the engine or frame.  Some folks use one of the bell housing to block bolts.  This will help all the body grounded electrical stuff work better.

 

The primary battery cable from battery to starter should be O gauge wire. Skinny 12 volt stuff doesn't carry enough amps for six volt.

It was the 30 amp fuse. Thank you for your help, I wouldn’t have known where to look

[Marcel Backs]

Wow that 2dr sedan is absolutely brilliant looking! Welcome! With a car like that this site is your ideal hangout for all that concerns it. ALL THE BEST M

[keithb7]

A fuse! Perfect. A simple fix. 
 

I tend to go straight to advanced troubleshooting. I do tend to jump past all the simple things, assuming folks have addressed them. My bad. 
 

Glad its fixed. Enjoy that car. It looks fantastic. 

[Marcel Backs]

A great electrical connection and switch cleaner is Deoxit D5. It can usually be obtained at electronics supply stores. It’s made by Caig Laboratories. M

Edited April 18, 2021 by Marcel Backs
Correction of crapple spellcheck

[greg g]

Now you need to do the other stuff so the fuse doesn't blow again.  If some circuit caused enough heat to burn out the fuse, something is amiss some where.

[greg g]

4 hours ago, chrysler1941 said:

And change the bulb to 6v ?

Nah it still works just a bit dimmer....