Circuit Breaker (and other) electrical questions

[JSabah]

On a ‘49 Plymouth....

 

(1) Does the circuit breaker care which side is supply and which side is load? There are no markings that I can see and the pictures I took before I took everything apart shows the power going to the taller/longer stud. I have several wires on the load side and it would be easier to put the loads on the longer terminal and the power on the shorter. 
 

(2) I’m now 12v neg ground - can I use the same breaker?

 

(3)  same question re the horn relay in the engine bay - can I use the old? (I do have a new/ rebuilt voltage regulator off a later model)

 

(4) I Am not planning adding relays for the lights (which I would normally do to give the old switches some relief) as I’m now twice the voltage so 1/2 the amperage so the wires and switches should be fine - am I thinking about this correctly?

[Sharps40]

Install a new breaker and relay.

 

Install new headlamp relays to maximize volts [brightness] at the lamps and to prevent overheating old or even new dash switches [fire hazard]

Edited November 19, 2019 by Sharps40

[JSabah]

If in a 6 v system there is a 30amp circuit breaker, would I use a 15a on a 12v system?

 

Similar question for the clock circuit- there was originally an in line 3 amp fuse, do I replace with a 1.5 (my clock has new 12v guts)?

[Plymouthy Adams]

your wattage stays the same though your amperage is half....you still consumer the same power.....and you always fuse the appliance/accessory per the requirements of the drevice/circuit......especially given your clock was not in any manner powered by the original system..

[JSabah]

if W=amp*V we can say that the clock originally drew 18W max as it had a 3 amp fuse @6 volts. If the power is the same (18W) but the voltage has doubled, then the amperage is half ... so wouldn’t a 1.5a fuse do the job?

[Plymouthy Adams]

did you not say that the clock is not an original 6 volt unit...now fitted with 12 guts....and if that statement is true, what was the source of the clock so to determine the value...and rating of the fuse is ONLY for the protection of the circuit not the absolute consumption of said device.  Most fuses power a circuit at a percentage over that of the circuit average draw  for protection...

[Sniper]

A 65W bulb (12v headlight) pulls 5.4 A per bulb, high beam.  35W on low beam so yes 15A breaker is fine.  Specs are based on a H6024  bulb, 7" round halogen.