The Stovebolt Site Forums The Shop Area The Electrical Bay Power question: Fuse panel and headlight switch

As I understand it from the detailed shop manual schematics, the stock '54 3100 only had that simple firewall mounted in-line fuse box for the Tail and Stop lights. the truck I recently bought is far from stock with a 350 chevy/auto trans/1 wire alternator, etc. Everything works well.
The previous owner installed a 12 position ATO type fuse panel under the dash which is great but did not label any functions.
I already made up a replacement fuse panel (not installed yet) and a relay (horn, led flasher, spare) panel. The fuse panel I built has both a Switched and an Unswitched section.

Questions/comments:
1) I want to get rid of that firewall mounted in line stock fuse box and fuse the Tails and Stops to my own panel.
2) Here's my real question and just having a hard time understanding it. If the 12 position fuse panel that the previous owner installed (or the one I built for that matter) has battery power going to every terminal then why would I need power going to the headlight switch? I understand that in its' stock version with no real fuse panel the factory ran power to the headlight switch.
As an example one of the terminals of the headlight switch is for the parking lights. Well if you are providing 12v to the lights at a fuse panel then you should not have to at the switch I would think.

Admittedly I am having a brain block on fusing a device in-line, vs fusing it at a fuse panel as well. Thanks

The headlights & tail lights are on different circuits. Its like 2 switches in one. The tail light fuse has its own power to the fuse & feeds the tail light part of the switch. The power wire feeds the headlight circuit.

I think of four electrical systems when I wire.
1. Ignition/starting
2. Charging
3. Lighting
4. All other components/switches

Typically most every component should be fused with it's own fuse panel fuse or a fusible link. With your 12V/V8 system, I do not know what headlight switch you have. Some headlight switches have a fuse at the power input. Some have internal thermal breakers/fuses.
As Wrenchbender says: Headlight switches have two power inputs. One for headlights and one for basically every other light. The one for the headlights connects power to the dimmer switch when “headlight” 2nd position is clicked.
The other power input, which usually comes from the tail light fuse, switches power to tail lights and parking lights when 1st or 2nd position is clicked. The rheostat dash light dimmer section sends power to the dash light fuse at variable output voltage. All depending on position or rotation of switch.
Again as Wrenchbender says, the headlight switch is unique. It has, sort of, several switches within. So for any "position" of the headlight switch, it is connecting power to light circuits. You must wire the headlight switch exactly like it is supposed to be wired per whatever switch you have. There are many diagrams for the standard GM headlight switch. Find the picture and hook up info that matches your switch terminals if you don't have a schematic already.

Other than Headlight/lighting:
Fuse panels have direct fuses and they have IGN switched fuses. Example of direct fused components are horn, dome, hazard....
Switched fused component examples are radio, wipers, heater, turn signal, gauges. You may choose a different idea depending on your needs or if you think you will never forget to turn IGN off.

Ign switched components are wired from the fuse panel to their switches, thru the switch to the component. The circuit is completed, thru the component's case and mounting, to intimate contact with chassis ground.

The fuse is protecting the wire, therefore wire sizing is important. Size the wire per amp draw and size fuse per that wire size. Many Google charts for that part.

This is way more info than you asked for. Please don't take it has a lesson to you. You are obviously plenty savvy. Any question about any part? Please ask. I learn by answering and seeing other answers.

On the 1954 Chevrolet truck with a original head light switch.
In the wiring harness, protection is provided for all wiring leading from the light switch by a thermal circuit breaker.
Lighting System, Desciption and Operation Read 2nd paragraph.
The light switch incorporates a 42 ampere Thermal Circuit Breaker to protect the entire lighting system.
I think you can replace just the Thermal Circuit Breaker if it goes bad.

Good info Jorb. The problem with all of this, and it's not unusual and has nothing to do with larry, is that we try to use old style systems and new style systems at the same time. Going from few fuses to many. Swapping motors and upgrading to 12V. Using an old light switch with a new ATO fuse panel, one wire alternator, foot start, push button solenoid start, key start, using an ammeter as a terminal block, adding relays, using relays as a terminal block, HEI, ballast resistors, thermal protected switch........ It gets confusing. I am as guilty as anyone.
Very hard to advise someone when you can't see the whole operation. I'm sure larry will absorb, reconnoiter and decide what to do. Hope he lets us help more and tells us his progress.

Guys..very helpful and no information is too much! So thanks. Sorry for the long post but maybe helpful to others now or in the future.

To answer some of your questions and then give comments:
A) First.....yes, having restored 6 cars through the years, you are correct. Compatibility amongst old/new systems can create more problems than sometimes the seem worth.
B)In the case of this truck, previous owner did a nice job with most things he did. It just came back from a month at Performance Eng'g in Hamilton, OH. Excellent shop with reasonable rates that actually specializes in (real) Cobras. Yes, there were 2 there (drool). I had pwr steering , pwr brakes, redone throttle assembly, backup light lever at the transmission, and some other non electrical things installed.

C) the HEADLIGHT switch in the truck is stock. I dealt with this very similar switch on the stock '40 Chevy Master Deluxe I did a while back. Yes...most of them have at least one fuse built into the switch. But never messed with wanting to add an upgraded fuse panel. I have the complete wiring diagram of the switch itself, ID'g where all the connections go. Seems that according to the master schematic of the entire truck (I blew that up to large and keep it on the shop wall) even the wire colors at the switch are still stock.
I remember even changing out that switch with an aftermarket repro for my buddy's 48 chevy car. Everything worked fine. But again no separate fuse panel.

D) On my truck I just finished installing the heavy duty headlight harness with relays as I now have H4 HID headlights in it. Everything works fine in that regard. I did not locate where on the existing fuse panel the 30 amp headlight fuse is but I will. By the way, I have replaced tail light and parking light bulbs with LED's.

E) And I understand the 1-2 positions of the switch, fused and constant-hot fuse sections (like the fuse panel I built), and absolutely understand AWG sizes. I tend to actually go overkill on that.
F) BUT...what wasn't making sense to me as mentioned in the original post was why do you need both a 12v source at the headlight switch and then another 12v at the ATO fuse for the same circuit (e.g parking light). If you are switching a circuit on, you have a 12v source, a switch, the load and then to ground. I did not think that if you have power at the fuse location, you needed a separate power source at the (headlight) switch. Schematically, is the 12v terminal at the headlight switch only powering the headlights and tail lights or is it the power source for the other stuff as well (dome, stop light, etc)?

So 3 things:
I want to do is get rid of the stock dual Tail/Stop in-line fuses on the firewall and instead have those fuses as part of the fuse panel I built.

I want to replace the existing fuse panel that the previous owner installed with the panel I made up. It is marine grade Blue Sea 2 boxes, junction posts, ground buss, with the switched-side box having a 70amp relay on it. It's def overkill and I built it from scratch. I just need to identify each circuit that goes to the existing fusebox which I will do.

If it is not this way now..haven't checked yet, have the power cable (AWG 4) for the fuse panel come from the starter solenoid post.

Lastly, you said:
"Ign switched components are wired from the fuse panel to their switches, thru the switch to the component. The circuit is completed, thru the component's case and mounting, to intimate contact with chassis ground"
When you say "thru the switch" are you referring to the ignition switch I assume?
When you say "to their switches" what switches are you referring to?

Thanks again.

I think I have misspoke and confused you. Looking at your era schematic, I should say there is only one power input to headlight switch.
As you probably know, that wire going to the tail light fuse is an output to the tail lights. My apologies. Schematic shows one power wire in from ammeter and the rest are outputs. They show the tail lights and the stop lights going thru a fuse on their way to the lights. I guess the rest is fused by internal protection. So one hot wire into H/L sw. All others are outputs to various lights. Some of the output wires go thru a fuse, then to the light. These would be unswitched fuses.

"Thru their switches" means: in one side of switch and out the other..
The components with switches, as I mentioned, would be wipers, heater, ...anything that has it's OWN switch. NOT the IGN switch.
In other words, a wire from a switched fuse to the wiper switch "in" terminal, another wire from the switch "out" terminal (you just went "thru the switch") then that "out" wire goes to the wiper motor.
In this case the ignition switch would have to be on and the wiper switch would have to be on to operate wipers. (you may have vacuum wipers). If a person has no electric switches on the dash except the Ignition switch, the comment would not apply. The comment was a general wiring comment.

These switched fuses would also be wired to gauges, the coil and components that don't have a switch and use the ignition as their switch or as you decide.

Do you by chance have a link to a picture of the complete wiring diagram of the switch?

Do you have a link to a picture of the above wiring diagram?

It is the power source for the other stuff as well (dome, stop light, etc)?
Figure 62

Here is a 1954-55.1 truck Wiring diagram
Sourc: 1946-1957 National Service Data Manual

So here is where I got the wiring diagrams:

For the switch itself I Googled images of the switch and there are numerous ones. I also think I saw it somewhere in the shop manual.

As far as the master schematic I definitely got it from the shop manual. It is also online with a search.

1954 Chevrolet Truck Light Switch

Most/all of the circuits in this switch are protected by a circuit breaker - it/they reset after cooling down. There are no "fused" circuits in the light switch.

I'm used to seeing the glass fuse at the rear of 55-59 Headlight switches I've had.

Maybe so for 56-59 ( 1955-2nd does not show a fuse?).

I think the original poster is referring to a 1954 light switch? No fuse is shown or referred-to in the shop manual (none of the 10 1948-55st switches that I have have a fuse).

bottom side of 1954 light switch (1947-1955st are quite similar)
top/bottom profile of this switch
No fuse(fuses) on/in/under this switch?

Yes, I understand about the protection method of his AD switch. Just mentioning the 55-59 style.

I edited/added 1955-2nd Task Force info into my earlier post - no fuse on that Task Force switch, I think. I do not have one of those switches,

If I remember, I'll check 56-62 manuals (in unpacked boxes in my garage).

Good info Tim. One year of the phenolic barrier shroud style with no glass fuse? I guess so. 55-59 manual shows switch as having two 25 amp automatic breakers built in and a visible 4 amp fuse in the panel light and rheostat circuit.

Listed as 55-59. I see 6V and 12V AD switches, in the aftermarket, that are like your pic of 54 but are listed as 47-54. I do not see any switches like the 55.2 you linked in the aftermarket. I guess it was redesigned a little and now suitable for 55.2-59.
Also there are 6V and 12V 47-55.1 style with a glass fuse offered.

"Carryover page? carryover part? 55-59 manual shows switch . . . "
What 55-59 Manual? Is it on-line?

The 1955-2nd Task Force switch shown at a link in my post above is no "carry-over" from the 1955-1st Advance-Design switch (they have significantly different overall appearance/design - the 1955 Task Force switch compared to the 1955 Advance-Design switch).

That 1955-59 Classic Parts switch is an aftermarket switch. However, it might indeed look like the original 56-59 switch?

I'll look at GM manuals tomorrow to see what they might show/describe for 1956-59, unless someone posts a link to one of those Chevrolet Truck Manuals.

I see that bartamos edited his earlier response while I was posting my reply.

I'll still look at 1956-1959 Shop Manuals.

Yes, took that out while you were typing. I revised my post altogether as I rethought.
55-59 GMC Maintenance Manual shows the little fuse from day one.
The fuse was added in the Supplement to the 55.2 Chevy Shop Manual. So one year, or 1/2 year, or premature page, with Phenolic barrier style with no visible fuse.
Maybe this is one of those things you can only see in books. Like a Dodo bird.
Glad we got that important thing covered. Whew!

1954 and 1955 light switch Top photo sure looks like a 54 truck switch.
I think the 54 car and truck used the same switch.

The 1950-1951 fuse box was in the same place, but it contained fuses for the taillights and stop lights only. Another change ... 42-amp thermal circuit breaker was now used in the lighting system in place of the 30-amp type previously employed.
Read More HERE some words yellow highlighted. "thermal circuit breaker"
It says in 1948-1949 There was one fuse for each high & low beam head light circuit and one fuse for each tail & stop light circuit on the firewall.
Another 54 looking switch the circuit breaker is the thing kind of in the middle, towards the back. The contacts are at the back end of it, the round thing at the rear end of the narrow strip of metal.

tclederman,
This is what I was kinda looking for 1955 Lighting Switch & Circuit Diagram Fig. 4 .(scroll down) -
I can't seem to find a Circuit Diagram for the 1954 truck switch. That is what I was really looking for.
bartamos,
Is correct, you can see the two 25 amp thermal contacts on the 1955 switch.

Source: Scroll to 1955

Jorb, be careful with 1955. There are two trucks 55.1 and 55.2. I was speaking of 55.2 when I quoted the 55-59 GMC manual re: 25 amp breakers and Tim sometimes speaks of 55.1 switch. I think we have a good understanding of the 55.1/55.2 switch design and redesign.
All the rest of your info is great stuff. 47-55 implies 55.1 and 55-59 implies 55.2.
The Chevy Supplement to 55.2 shows a fuse in the schematic and speaks of the redesign.

Right..all the more reason to have a capable fusebox.

Yes that top picture is for a 1954...at least that is what mine looks like.
Yeah so Google this: 1954 chevy truck headlight switch wiring diagram
There are a number of images.

Sorry, bartamos.

The fuse locations in the first photo that I posted (and, misinterpreted) are clearly visible.

Thanks for the clearer picture, jorb. I had not tried to blow-up my link's photo , no fuses are visible, BUT the fuse holders are very clearly visible.

So,
- no 47-551st light switches had a fuse; and,
- all 55-2nd-59 light switches had 2 fuses?

larrygk has probably left the house, but none of this 55-59 discussion changes the fact that his 1954 light switch's circuits are indeed protected by an automatically-resetting circuit breaker build into the switch.

thanks tim...I'm still here! good info on the circuit breaker. Didn't know it was auto-resetting.

Tim, no sorry needed. I think you thought you were wrong when you were right.
Don't see any pics with empty fuse holder?
2 fuses?= one visible and one breaker?

Summary, again, from the manuals:

47-55.1: old style metal switch, 6V, built in protection. No actual fuse.

55.2: new phenolic barrier design, 12V, built in protection. No actual fuse.

56-59 Chevy: new phenolic barrier design, 12V, built in protection. 4amp additional visible fuse.

55-59 GMC: Maintenance Manual shows the Chevy 56-59 style and design.

Built in protection= Built-In Automatic Thermal Circuit Breaker (various amps depending on year)
This device would "automatically" reset and would also function intermittently to maintain vehicle operation, if possible. 42 AMP breaker? WOW!

This fuse has become too much of an issue, probably caused by me. It's a tiny 4 amp glass fuse they decided they needed for the dash light/dimmer circuit probably because the thermal breaker device was not covering it since it was a small variable load.

Larry, let us know how it all turns out. Thanks

Now, I am seeing only circuit breakers in that 1955 Task Force switch that Jorb and I posted links to?

http://chevy.oldcarmanualproject.com/electrical/wiring/pdf/55csm1204a.pdf

I am am getting old and addled.

I'll check the later manuals, too.

1958 and 1959 manuals show a different style lighting switch (from the 1955-2nd switch). All but one 58/59 circuit are protected by two 13-ampere thermal circuit breakers.

1 breaker for the headlamps & parking lamps
AND,
1 breaker for all other lights EXCEPT the instrument panel lights

AND, the instrument panel lights are protected by a fuse at the rear of the light switch (the clips for that fuse can been seen in that Classic Parts switch).

I have to now go look for the 1956 Truck Shop Manual (which is only a "Supplement" to the 1955-2nd Truck Shop Manual), to see if the 1955-2nd switch or the 1957 and later switch was used in 1956.

It should be noted that if the switch changed between 1956 & 1957, knowing the switch-over date is impossible - GM did not change models on January 1st and did not stop using older parts until they ran out (as long as the older part fit/worked in the place of the newer part.

larryg's question has been answered: A-D trucks (1947-1955-st series): no fuses associated in/on the light switch.

This question then moved into Task Force trucks light switches, and if fuses were added to the lighting system.

bartamos has nicely outlined lighting-system circuit-breakers and fuses (or not) on Task Force trucks:

Task Force trucks
- 1955-2nd series: no fuse on the light switch
- 1956-1962: one fuse at/on the rear of the light switch

1956 Shop Manual:

"The 12-volt electrical system on 1956 trucks is basically the same as that used on 1955[i]-2nd series, Task Force, trucks.

The master light switch on the instrument panel has been improved through the addition of a fuse which protects the instrument panel light circuit."

Just in case anyone still wants to know.

I am am getting old and addled.

Tim, I think I'm in the same boat.
When you posted this LINK 1 I just saw the picture of the switch,
I never scrolled down to see the Fig. 3 Lighting Switch Circuit Diagram.
Then after digging around the internet for awhile I posted this LINK 2
Which is has basically the same images you posted. Wow!
I need a drink.

One tidbit on the text info in the link that you posted.
On the 1955 Chevrolet Truck 2nd Series light switch a safety feature was incorporated by basically splitting the switch in half.
One circuit breaker protects the headlights and parking lights, while the other circuit breaker protects ALL the remaining vehicle lights.

For example:
You could have a short on the rear lights and the headlights and parking lights would still work.

On the 1954 Chevrolet Truck light switch ALL the vehicle's lighting protection goes through one circuit breaker.
If you have a short anywhere you could loose headlights.
Less Safe, especially if your driving at night with sunglasses on.

We'll get it right, jorb (actually, we GOT it right).

Both of use like to find/show documentation, and THEN postulate on possibilities/oddities/memories and dreams/desires.