How to check a circuit breaker?

[fjz]

I am in the process of re-wiring my 48. Attached to the gage panel is a circuit breaker which is a sealed unit with 4 posts and I can not find listed in my catalog. It appears to be fed by a short wire from the amp gage to post #3 which is connected to post #2 via a bar. Not sure what 1 and 4 feed. Would like to check it before installing the dash. Thinking of connecting one side of my 12v garden tractor battery to post 3 and the other side to my test lite which I can touch on posts 1 and 4. Is this OK?

[zzlegend]

Have you tried a search for a wiring diagram? Maybe this will help. And maybe not.


https://www.classiccarwiring.com/194...iring-diagram/

[JSeery]

48 wiring diagram. There should not be any connections between the circuit breakers (there are two within one cover) and the gauges. The connections should be to the lighting control switch.

There should be three terminals on the circuit breakers, labeled B,H & A. All of these are Hot all of the time.

B terminal: Wire from Battery via ammeter, Wire to Voltage Regulator, Wire to Ignition SW & Wire to Cigar Lighter.

H terminal: One wire to a connection on the Light Control SW

A terminal: Wire to a terminal on the Light Control SW, Wire to the Brake Light SW & Wire to the Pillar Light SW.

Not sure what connection a 12v source to the CB would accomplish. This is a 6V positive ground system. All of the post on the CB should be HOT (as in 6v present) any time the Battery is connected. The CB should open when there is a short or overload. I guess if you wanted to check it you could short a wire connecting to terminal H or A. But be prepared to a lot of sparks!

[JSeery]

Second thought, is your 48 converted to 12v? If so, what you are looking at is most likely a voltage drop and not a CB. There really shouldn't be a CB directly to the gauges.

Does it look like this? That would be an add-on of some type, like a elec fuel pump.

[fjz]

Thanks JS. I am 6v and the CB is original. It is a sealed unit but may come apart by lifting tabs. Must be fuses of some type within which control posts 1 and 4. 1 has YR,G, and Bl wires. 4 has Y, YB and YBl wires.

[JSeery]

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Well, YR should go to the light switch, G to the brake sw & Bl pillar lights? Y would be from the ammeter and to the VR & cigar lighter, YB is ignition sw, can't see YBl on the diagram on my phone good enought to tell.

[rotorwrench]

Is this a truck or a car? Here is one like you describe for a truck. https://www.ebay.ie/itm/1948-50-FORD...-/112640274262

It is marked for the H, A, & B. The other is not used. An ohm meter can check the CBs for continuity. No continuity, no good.

[JSeery]

Good point rotorwrench, that would make a difference. It would also be a different wiring diagram, but basically the same wiring connections.

(not my photo)

[fjz]

Thanks for the replies. Mine is a car and the CB is more rectangular. Did not have an olm meter so I checked it with test lite I mentioned previously. Power going to all terminals and is now ready install dash once the new headliner is in. I am curious as to what is inside the CB, fuses I suspect, and will take one apart when I get another.

[rotorwrench]

Bi-metalic strips. When they get hot, they open the circuit. When they cool back down, it closes the circuit again. It tells you real quick if you have a short in the headlight wires.

[Gick70]

Do I need to change the wiring if I go to 12 volt system?

[rotorwrench]

Only if it is unserviceable. The wire gauge is larger than needed for 12-volt but it will still work as long as it's in good shape.

[Frank Miller]

The two connected terminals are the input and then it protects two circuits. To test them you need to put a load on them. !2 or 6 volts do not matter but it is amperage that opens them up. If you wire up a couple of headlights to them and leave on for 30 minutes you're probably ok. If you have a 20 amp meter to wire in the circuit to see how much you're really drawing all the better. You could add lights until they trip to see what they are rated for or actually working at. These can fail but it is rare.

[fjz]

Thanks Rotor and Frank. Now I know and if I have an issue down the road I will know where to look.

[rotorwrench]

If a person gets continuity through them, the best test is to turn on the affected circuits which is mostly all the lights on the older cars. A person has to short a hot wire to ground to see if it pops or if the wire burns up. That kind of test is better done with a wire that can be sacrificed without ruining a good harness. I usually don't worry about them too much. They are generally reliable and last a long time. When they go bad, they usually have no continuity through them. At least this has been my experience with them. Most of my Harley Davidson motorcycles have them too. Big trucks used them for many years.

If your lights go off & back on for no apparent reason, it's likely got a short in the wiring somewhere and it's tripping a breaker. They can sometime do this when they get old in which case it's time for a new one.

[Paul Bennett]

I'm afraid you are overthinking the circuit breaker. Simply wire it into your car and enjoy your work.

You don't have the load equipment to test the breaker plus you don't know what specifications to use. Plus, circuit breaker rarely rarely go bad unless they are abused and a home test could be the abuse which thwarts your purpose.

[Frank Miller]

Originally Posted by rotorwrench

If a person gets continuity through them, the best test is to turn on the affected circuits which is mostly all the lights on the older cars. A person has to short a hot wire to ground to see if it pops or if the wire burns up. That kind of test is better done with a wire that can be sacrificed without ruining a good harness. I usually don't worry about them too much. They are generally reliable and last a long time. When they go bad, they usually have no continuity through them. At least this has been my experience with them. Most of my Harley Davidson motorcycles have them too. Big trucks used them for many years.

If your lights go off & back on for no apparent reason, it's likely got a short in the wiring somewhere and it's tripping a breaker. They can sometime do this when they get old in which case it's time for a new one.

I have replaced a failed one on a Harley ignition. It would work for a bit then fail. The points may have gotten some corrosion creating some heat to open it up. Did not dissect it to figure it out.

[cmbrucew]

FM

On the Harley, they mounted them upside down and they filled with water.
The head light one failed for me on interstate 15 between Victorville and Barstow.
No street lights.
Bruce