The Stovebolt Site Forums The Shop Area The Electrical Bay Can someone please refresh my memory?

Hi!

I was looking at the wiring diagram for my brake lights, and I see that the juice does indeed come off of the headlight switch.

Is the brake light circuit fused by the switch? If not, Should it be?

If it should be fused and it's not, I'll put a fuse in-line when I rewire it.

Thanks in advance,

-Brendan

the light switch has a main fuse as well as 2 bimetallic contacts [1=front, 2nd=back] that will open if there's too much draw

only add-on fuses that are useful is on optional accessories

Bill

The only lamps that are protected by a fuse are the instument panel lamps. All the others are run through the 2 circuit breakers that are built into the switch. A fuse shouldn't be necessary for that circuit. Having said that, I have mine wired to the fuse block so that the tail lamps are on when the ignition is on. I have LED tail lamps so the constant on is not an issue.

I can't believe that the power for the brake lights goes THROUGH the head light switch, maybe the wire that carries the power to the headlight switch continues from there to power the brake light switch, however. Are you sure you're reading the diagram correctly? Or did you mean the taillight circuit?

the brake light power goes through the turn signal switch.

Thanks Bill and Bill.

Wow. This "Bill" thing is gonna get confusing.

I'm going to have to make sure that this switch that's in there has the proper hookups and breakers (I don't see why it wouldn't, but then again, I know my grandpa), and that the brake lights are hooked to it.

Zenish: What turn signal switch? That's why you have arms!

Seriously, though. They didn't even bother putting turn signals on until the mid-to-late fifties, and they weren't mandatory until 1961 (at least in Michigan).

On those old trucks, the brake lights ran through the headlight switches, seeing as they didn't HAVE turn signal switches. That, and I just redid my switch, and trust me when I say that the brakes WERE NOT routed through the bloody thing when I tore it down.

Are you saying that the brake lights won't come on unless the lights are on? If so, it's misswired. I still think you must be saying brake lights when you mean taillights. No way should the brake lights(or light if it's a stock 1947) have anything to do with the headlight switch. A hot wire goes to the brake light switch and another wire goes from the other terminal on the brake light switch to the tail light assembly. The tail light is wired from the proper terminal on the headlight switch to the tail light assembly. In other words, there should be two wires at the tail light assembly going to different filaments, one the tail light wire and the other the brake light wire.

I'm assuming this is an AD truck. If so the power to the stop light comes from a terminal labeled "stop" on the light switch. It then goes through a fuse on the firewall, then to the brake light switch then on to the brake light.

Thank you Cletis,

Is the STOP terminal just a buss to the power terminal on the switch?

the power for the stop lights comes off the headlight switch - regardless if the switch is on or off - it, along with all the other lights is protected by the bimetalic contactors [like circuit breakers - get hot the metal bends away from the contact, as it cools it straightens back to making contact] - if any have a fuse between the light sw and the stop sw, it's an add-on or an option, fuse panels weren't standard until the TF years, and even then didn't get them unless there were some optional elec items installed

doesn't matter what year it is, the light switches are alla same - when turn signals are added, the brake light wires still go from the light sw to the stop light sw and are routed from there thru the turn switch to the lights - power still comes from the main light switch

Bill

Then I should and do apollogize to Brendan. So the light switch is the circuit breaker for all the lights.

Cletis: It's a '46 (Victory), but yeah.

Bill: Thanks.

Baldy: Have a peek at the diagram .

another wiring link from bolt memeber

ad wiring link

As I stated above, there is a fuse box on the firewall of advance design trucks that contains a fuse for the brake light circuit. It also contains a fuse for the tail light circuit.

ref: Chevrolet Truck Shop Manual reprint, 1948-51. Also shown on the 1954 Chevrolet Truck Wiring Diagram. Also shown on the diagram for a GMC that Joker linked to.

There is one attached to the fire wall of all the AD trucks in my inventory. It's place in the curcuit is between the light switch and the stop light switch.

That diagram is for a pre AD truck and I think that the truck in question is a 46? That light switch and wiring is definitely different than the AD. I was surprised to see that the ignition feed and the gas gauge feed are unprotected. All the cab interior lighting appears to be protected by a fuse in the light switch. I don't believe that the light switch has the bi metallic breaker.

I see that the diagram has that crazy polarity reversing switch. I think that the diagram must be older than 1946.

Wow. Looks like I stirred up a hornets nest with this one!

Cletis:

The truck in question is a 1946 Victory Series ("Art Deco") Chevy.

While the '46's and Advance Design trucks share many mechanical features (same differential, brakes, et cetera), the electrical system is pretty much the same as the earlier trucks'. There wasn't a fuseblock there. The only fuses were in-line, on the light switch, or not installed.

That having been said, I do have an AD Brake/Tail fuse box that was in a big box of "old chevy stuff" that came with the truck. I also have another dimmer switch and a crapload of old bulbs that don't work.

Truckernix:

It's the one in the 1942-1948 Chevy shop manual. I did notice that polarity switch when I was looking it over, and assumed that it was originally for something older, but was close enough to reuse.

The Headlight switch in my dashboard was replaced at some point (it doesn't have the correct knob), so I have no idea what I'll find when I pull it to hook up the new wires. I'm assuming (I know, dangerous) that it was sometime in the sixties or seventies based on the type of plastic that the knob is made out of.

The gas gauge was rewired at some point (and desperately needs redoing again) and whoever it was that installed the new wiring used an in-line fuse holder, so that's protected.

When I finally get around to doing a complete rewire on this thing, I'll be including some fusable links and relays.

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So, now that I'm completely con-fused (pun intended), what did we decide?

Fuse yes? Fuse no?

If yes, how big? 15 amp is what I was thinking. I'm using 14 gauge wire on a 6v system.

Brendan, I don't have an earlier diagram. If your wiring is already a rat's nest it might be a good time to go ahead with the new harness.

I'm in the process right now with my '56. I'm using a Hot Rod Wires harness. If you want to stay closer to stock check with the specialty vendors.

Brendan,

The typical 14 AWG is rated for 20 amps, more than adequate for your brake light circuit. Standard wiring practice says size the fuse to protect the wire, so a 15 amp fuse would be appropriate. Many older rigs had little circuit protection, but a little in-line fuse would be cheap insurance for old #7.

Stuart

Hey Stuart, where have you been hiding? Haven't seen you in the 'bolt for a few weeks now. It's good to have you back.

Tiny,

Catching my breath...thanks for the kind words.


Stuart

[pokes hornets' nest with stick]

[runs like the wind]

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Okay, so the consensus is: Fuse. Rinse. Repeat.

Will do.

I went and bought some fuse holders today, and I've got enough solder and heat shrink to choke a horse.

Thanks for the help, guys.

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Stuart! How the heck are ya?!

Long time no see!