The Stovebolt Site Forums The Shop Area The Electrical Bay Headlight Switch Power

1951 3100

Perhaps I'm reading this wrong, so somebody enlighten me.

Everything is 12 volt, (new gauges, new radio, dome light, indicator bulbs lights, etc.), all new wiring. No harness, I'm doing all my own wiring. Have a 12-volt generator.

I do have the wiring diagram for my truck, blown up big size. I did buy the original design repro headlight switch, looks exactly like the switch that came out, (it was/is a non-fused switch).

Power TO the headlight switch, comes from the ammeter? Wiring diagram shows it that way.

I get it that power from the battery runs THROUGH the ammeter and then on to the voltage regulator. That makes logical sense. And I see how this could power the headlight switch, doesn't seem logical, but it would
work. Why not power the headlight switch from the 'B' terminal of the ignition switch? I will have power from the battery, direct to the 'B' terminal on the ignition switch, and from there on to a 8-circuit always powered fuse panel. And a wire from the 'I' or 'A' terminal on the ignition switch to a 8-circuit fuse panel that gets powered when the ignition switch is turned on.

Why not power the headlight switch from the 'B' terminal of the ignition switch? I do intend to use the headlight relay kit also, but that appears to happen AFTER the headlight switch.

Does my question make sense?

Mike

Doesn't make sense to me. Bypassing the ammeter means the ammeter is no longer serving it's purpose properly. Follow the wiring diagram.

Since you are installing a new headlight switch and new wiring, there is no need for relays for the headlights. (unless the dimmer switch has excessive resistance; if so, you should replace it too)

B battery, I ignition, A accessory. Anyway to the question, as Gord said, the ammeter is for measuring current. So the headlight/switch draw is after the ammeter.

To answer your generic question, A person can get positive/hot power to anything, from anywhere they want. Depends on if you want to get things fused and use the ammeter. Electrics were a little low tech back then. Lacking in fuses and fusible links. They got with the program later on. Your AD will run just fine if you follow the wiring diagram.

Some folks like me, don't like ammeters. Don't like running all the power up under dash onto one terminal. Voltmeters make more sense to me. 99% of all vehicles have voltmeters now....or lights, which are a better warning. Jerry would calI them Idiot lights, I like annunciator better.

They both have their uses. Ammeter tells you whether you're charging or discharging, voltmeter tells you how much voltage your battery is putting out. Of course, if your voltmeter reads low, obviously you're not charging, so the ammeter becomes pointless. If a voltmeter dies, the truck will still run.

Gord&Fran,

I am not by-passing the ammeter. It is wired exactly as the wiring diagram shows. And yep, every switch, terminal, wire, connector, gauges, they are all brand new.

My concern, and it shows this on the wiring diagram, is that the headlight switch is getting powered from the same wire that does pass through the ammeter. If that's how they wired it from Chevy back in 51, then so be it. I'm not trying to re-engineer it. (HRL would chastise me if I was). This IS what the wiring diagram shows.

Logic is just telling me something else.

bartamos,

I understand the purpose of current running THROUGH the ammeter. I'm questioning whether this is how the headlight switch is powered. According to the wiring diagram, it is. Obviously, 12volt power is running through the ammeter. It's kind of a straight run from the battery through the ammeter to the voltage regulator.

Wire from the battery +, goes to ammeter +, ......wire from ammeter - goes to the voltage regulator B terminal. But along the way the headlight switch has tagged on to this ammeter - wire going to the regulator. Diagram shows no other power wire going to the headlight switch. You have the terminals on the h/l switch for dome, tail, instrument, etc., which would be all out-going.

In my hard head, I'm thinking there needs to be a true hot-wire, from my fuse panel, that would power the headlight switch. Maybe not.

I shall investigate further.

Mike

Mike,
In reading your post at the beginning of this thread you stated your headlight switch "was/is a non fused switch." I don't know about your replacement switch but the original switch had a bi-metallic thermal fuse or circuit breaker in it. That gives you some degree of protection from a short in the headlights, tail lights, gauge lights and dome light. And current use in any of those systems would be indicated by the ammeter.

As an example, let me share something that happened to me when I went for a test drive in the process of restoring my '50 COE. I had replaced the original wiring with a harness from Rhode Island Wiring and used the original head light switch, maintaining 6 volts. Suddenly, the ammeter was gyrating violently from normal slight charge to marked discharge. It would flip from one side of the gauge to the other every second or two. This was the thermal circuit breaker doing its thing, letting excessive current through, overheating, and then breaking the circuit, cooling off and then reconnecting. Of course, I had a 1/2 inch wrench handy to unhook one of the battery cables. I could detect that dreaded smell of burnt wires. It turned out that when I installed the dome light, I had pinched the wire between the light housing and bezel and it took a week or two before the pinch worked its way through the wire insulation. The only casualty was the dome light wire so the circuit breaker protected the rest of the wiring harness. I got to practice replacing the dome light wire through the A pillar again.

Since you have gone to 12 volts you may be interested in redesigning the wiring in order to use accessories and in doing so you may want to use a convenient fuse panel. But the factory wiring was sufficient for the original intended purpose.

Kent

I say that it is not fused, it may very well have the internal circuit breaker built in it. I bought it from Classic Parts. They offer the repro 'original design' and the repro 'that looks like the same, but some modification will be necessary' one. I went with the 'original design' one. Looks exactly like what came out of the truck. Matched perfectly. Every wire that has been run, has soldered terminals and heat shrink on every one them. I'm all about overkill.

Note, in my original post, that I did install, under the dash, an 8-circuit 'always powered' fuse panel, AND an 8-circuit fuse panel, that will be powered by either the 'I' or 'A' terminal coming off the ignition switch. This way I have some items that will always be 'hot' (cig lighter, horn, etc.), and some items that would need to be 'hot' once the ignition switch is turned on (gas gauge, radio, etc.).

As it stands, according to the wiring diagram, there is no direct 'hot' wire that powers the headlight switch. I could certainly send a 'hot' wire from the 'B' terminal on the ignition switch, directly to the headlight switch, and the headlights would come on without the ignition switch needing to be turned on. That, makes sense to me. But that ain't how/what the diagram shows.

I appreciate everybody's thoughts on this, but the question has not been answered. Let me ask it this way....Where does the headlight switch get it's power?

I'm not wanting to be difficult, I just want to do it correct, FIRST time. And wired according to the wiring diagram, may very well be correct. Just doesn't look that way.



Mike

As I said, I believe these old trucks are challenged as far as wiring, fuses, ammeter. I don't want to get into how I would rewire them.


Quoting you:
"Wire from the battery +, goes to ammeter +, ......wire from ammeter - goes to the voltage regulator B terminal. But along the way the headlight switch has tagged on to this ammeter - wire going to the regulator. Diagram shows no other power wire going to the headlight switch."

"Where does the headlight switch get it's power?"

Answer, as you have said many times, as we have said, if you want to follow the 1951 diagram, H/L switch gets it's power like the diagram says. From the ammeter. Physically, if that's what your hang up is, you can wire it right from the ammeter terminal, or any other tap-in place. They are all the same power. A terminal block, a terminal of some other component, a splice, whatever. They DO NOT show a fuse to the switch except some have a little fuse for dome and brake and they have the automatic thermal overload contacts/switch. You have added a well thought out fuse panel with always hot and switched hot fuses. This is good. But the wiring diagram you say you are following does not have that, so you need to wire it per a newer wiring diagram that has a fuse panel, if you want a how-to on that area.

On the next era up (TF), they use "tell tales", a light bulb. No gauge, no ammeter, no voltmeter. They wire the pos battery to solenoid, then chain or terminal block or "chassis junction" or bounce off a component to wire directly to H/L sw, Ignition Sw, Voltage Regulator. They did add a few fuses.

Up into the 70's, still tell tale/idiot lights/annunciators . You could get gauges as an upgrade.


"Where does the headlight switch get it's power?" maybe another way to answer it is: Directly from the battery, thru the ammeter. Routing and actual to-from is a direct wire or a "tagged on" wire. Tagged on meaning: pick off the power anywhere at, or after, the ammeter downstream terminal. Whew!

bartamos,

You get it....and you got it.

Your answer confirms what I thought. Yea, I deviated a slight amount from the original design with the fuse panels, but that's only for my peace of mind (and it's a good safety measure).

Thank you, and everybody else, for their insight. I knew what I was thinking, it was the 'explaining' that was iffy.

(and so far, HRL hasn't gotten me for over-thinking this.....he may yet though).

Mike

He will be notified via secret PM.

Drop me a PM or a phone call- - - -no way I'm getting in the middle of another whizzing contest on the open forum!
Jerry

1) I cannot believe that I read all of that. I was certain, early on, that it would not end well, yet I read on.
2) My disappointment is only in myself. I knew better, yet I still read on.
3) My only hope is that I someday I find a magic lamp with a genie (preferably of the smoking hot variety) inside who will grant me 3 wishes.

They will, all three, be this: "Please give me back the several minutes which I have lost forever by getting sucked into reading one of HRL limericks!"
Yes all three wishes the same. I feel damaged just that badly.

Oh, I too was sucked in and read it I did do, and grinned and laughed all the way through.

So at the end of this discussion I'll share that I also considering the wiring and considered fuse panels and relays as I had read the many posts on wiring and thought that I too might improve on the original. In the end, I bought new switches for the lights and ignition, ordered all of the correct color and gauge wiring, found the flag style terminals and wired it just like it was and according to the wiring diagram. I guess my logic is "why fix something that isn't broken and has worked for as long as I've been alive".

Once you start reading it, you can't stop because you need to know how it ends. Just like this thread.....:)

If you see that it is from HRL, do yourself a favor and always skip to the last line. That is where you will always find the corn.
BTW, he is not responding as he knows that it may bring me solace. Solace is not his strong suit.

LOL!!

Carl, as always, thanks for the lefthanded compliments! Rattling your cage is one of the big reasons I enjoy hanging out here!
LOL!
Jerry

Why, Why am I still reading in rhyme
Is it that it's Sunday morning and I do have time

Nope, enough of this!!!

Don't look at the Greasy Spoon, whatever you do!
LOL!

Uh, I just wanted to know about some wiring. Now I'm gonna be held accountable for this.

I had a another question or two, but I'm a little afraid to go there now............

Mike

Mike, slow weekend and the children wanted to play. It's just part of the charm of Stovebolt.

Now I'm a 'rogue rookie'.

Been turning wrenches since about 1987. Guess I'm new at it..........

I'm good with it.

Mike

Well Mike, I have met Jerry a few times and will see him again in about a month at the Homecoming.
He is quite entertaining and can be a little harsh at times, but a wealth of knowledge.

Yes Jerry, I read the whole thing and am wiping the laughing tears from my eyes.
Picking your motor up Friday.

Don

I'm good with it. It's all in fun. If I'm gonna dish it out, I better be ready to take it.

Other thing I was questioning, does the ammeter HAVE to power the headlight switch? Another way to look at it, what if the headlight switch is powered through the fuse panel and the ammeter wires never run to the headlight switch. The ammeter will still be wired incoming from the battery and out to the voltage regulator. My understanding is the headlight switch, being the draw that it is, has effect on the D-C on the ammeter gauge.

Just curious, (really just thinking outside the box).

Come on with it bartamos, I see the wheels turning there.

Mike