Circuit Breaker Question

[Dan D.]

Does anyone know what the headlight switch circuit breaker rating should be for 53/54 6V cars?

I have a need to know.

Thanks,
-Dan-

[Philip P.]

Re: Circuit Breaker Question

Dan

I think if it is the same as a car it is 30 Amp. here is a link for the 53/54 shop manual that talks about it. Hope this helps http://chevy.oldcarmanualproject.com...ical/12_42.HTM
Phil

[Dan D.]

Re: Circuit Breaker Question

Thanks Phil,

This is what I was looking for and I think it is accurate for Corvettes as well. Lots of other good info in this too.

-Dan-

[Thomas H.]

Re: Circuit Breaker Question

Wow, 30 amps. I'm wondering if they are using 10 gauge wire as anything less then that is not rated for 30 amps. But then again, Dan was talking about 6 volt systems.

When I did my study into headlight switch breaker ratings, I believe the breaker internal to the headlight switch in my 60 was rated at 17 amps (12 volt system). The repop switch I had was tripping at 10 amps which was causing my headlights to go on and off while driving on a dark road, not much fun.

Breakers / fuses should be rated not only to limit the current to the circuit they are connected to, but to also protect the wire used to connect the circuit. You want the fuse to be the weakest link, not the wire......



Tom

[Dan D.]

Re: Circuit Breaker Question

Hi Tom,

The feed wire to the switch on 6V systems is 10awg. But the wires coming off the switch are 12, 14 and 16 awg. Go figure.

But these are cloth covered wires - not PVC - and will probably handle higher currents better. And the codes for home wiring are probably more conservative than what the auto industry uses, especially in the early and mid 50s.

I have recently tested an original untouched 59 switch and found that the breaker will hold at 15A and trip at 17.5A, which is in line with the chart in ST-12. By the way that chart in ST-12 has several problems - it is not that all accurate.

Tom, I have been repairing three 1954 and a 1959 switch for other members. This includes drilling out the rivets (eyelets) in the rheostat, replacing them with brass screws and soldering all current carrying connections. The corrosion under the heads of the rivets mandate doing this, as it is the only way to restore electrical continuity. Dissimilar metal problem - galvanic corrosion.

We may have done some work in parallel -wish I had known that you have some breaker data.

I have built a test fixture for doing this work. It incorporates a 30 amp -12V power source, current meter, and resistor load bank for testing these things. Will post a photo of it in a day or so.

-Dan-

[Thomas H.]

Re: Circuit Breaker Question

Hi Dan,

We definitely went down similar paths. I wrote an article for our chapter newsletter on my repop switch

http://clubs.hemmings.com/DelValNCRS/August_2013_Del_Val_Chapter_Newsletter.pdf

It is good to know you are repairing the originals as they are built better then the new ones.........

Tom

[Dan D.]

Re: Circuit Breaker Question

Hey Tom again,

I know you wrote that article (lights out). You posted it in a thread last fall. Should have gone back to you sooner.

In a recent thread on repop switches, one supplier responded that they did not test their switches. I find it hard to believe that a supplier does not test electrical assemblies like these switches.

I'm not sure if you can 'adjust' these breakers by bending the arm. It is real easy to do on the 6V units, and I can set them to any current I want. I'm sure that is how the factory did it. Interesting, the three 54 switches I have, which were all reported to be inop, one breaker opens >30A, one opens at 12A, and the third one was permanently open - no contact at all. Needless to say the owner of that switch said that none of his lights worked. And none of the rheostats worked, although one worked intermittently. I now have 2 of the 3 all repaired and tested - was just waiting for some guidance on where to set the breakers. Now I know. The third one will be disassembled tomorrow. This is good medicine when it is snowing, blowing, and freezing. Basement workshop - nice and warm, will lighted, radio playing. I will post some photos tomorrow.

-Dan-

p.s. Your "lights out" article was good enough to be in the Restorer.

[Philip P.]

Re: Circuit Breaker Question

All, This may be of interest.
Philimg001.jpg

[Dan D.]

Re: Circuit Breaker Question

Got some photos of my test set-up.

This is my power and current set-up. Built on a 1'x' x1/8 thk. Alum plate my son-in-law gave me. The unit in the rear is a 12V 30Amp switching power supply (from E-Bay - <$30). Right front is an old Simpson current meter with 5 separate current ranges selected by screw posts. 1A, 2.5A, 5A, 10A, and 25A. Been laying around for 4 or 5 decades. Time I put it to use. Left front is a switch box I made to select the different current ranges. All are fused at the specific current range that is selected so I hopefully will not blow up the meter. Second photo is the resistive load bank, also built on a 1x1x1/8 plate. Switch under test is at the left front. I can plug in various resistor strings to get most any current up to 25 Amp. I can push to 30 Amp by bypassing the meter, and will have to do that for the 6V switches. I use a small muffin fan for cooling the bank.

(Excuse the last photo. Had a terrible time uploading these photos. It should be easier).
-Dan-

Test Setup (480x640).jpg

Load Bank (480x640).jpg

Power Source (640x480).jpg

[Thomas H.]

Re: Circuit Breaker Question

Good set up Dan. Perfect for verifying operation of the breaker in those older headlight switches.

You normally can not adjust the trip point of the breaker by bending the bimetallic element. If anything that reduces the pressure at the contact points which in turn increases the resistance at that point, which is not what you are trying to do.
On these types of bi-metallic breakers, the trip point was set by t******* the width of the long "arm" (for lack of the technical term that escapes me right now....). Doing this will cause the resistance of the arm to increase, thus increasing the heat within the bimetallic element and causing it to trip (open) at a lower current. It doesn't take much material removal to have an impact on the trip point, we are dealing with milliohms here..........

I spent several years as the engineering manager at a company where we developed electronic circuit breakers where you could tailor the trip point, inrush current as well as several other parameters. All computer controlled. We could hold trip points to tenths of an amp over a -40 to 85 deg C temp range while passing up to 30 amps of DC at 28 volts. Applications were for multiplexed power systems in yachts and general aviation aircraft. I spent many hours in front of resistor banks very similar to what you have set up. Burnt up a lot of MOSFETs along the way too............... I can still smell them.............

Enjoy!

Tom

[Dan D.]

Re: Circuit Breaker Question

Hi Tom,

I am not bending the bi-metallic arm, rather the piece that the arm is welded to. That increases or decreases the tension the arm has on the contacts. This tension was all over the map on the three 1954 switches I currently have, and I can adjust this tension, and the trip current, very easily. It amounts to how hot the strip has to get before it relaxes enough open.

But the 54 switches are quite a bit different than 55 and up switches are. I have not tried to adjust any of these, and was asking the question if one could adjust them, as I don't see anything one could bend. So I'm sure you are correct in this regard.

There is another benefit from the power source/current plate fixture. This fixture can be used to power up a car - except for starting it of course. One can set this plate on the fender and connect it to ground and the battery feed wire to the car, with the battery dis-connected. So you are feeding the car from the power source, all the while monitoring current draw. This is desirable if you have just restored the car, replaced harnesses, trying to isolate a short circuit, or trace down a condition where fuses are randomly blowing. You have a maximum 25 amp source, which will not damage anything. And you can easily measure just how much current anything in the car is drawing, and quickly shut off power if necessary. I have done this on my 57 and I know just how much current every light in the car is drawing. Pic below of 54 switch.

-Dan-

54 Headlight Switch.jpg