1948 Plymouth P15 Fuses

[Pep48]

I'm a bit confused...is there only one fuse (in the light switch) which protects the entire

wiring system??

 

If so I'd like to add additional dedicated fuses via a fuse box.

[Sam Buchanan]

If your wiring is still original.....yes.....one fuse on the headlight switch. It was a different world back then. 

[greg g]

Geese, you got lights, ignition, heater fan and horns!  What more do you need? Some late 48 early 49s supposedly had a 30 amp self resetting circuit breaker mounted to the inside of the fire wall.  My 46 has only the one fuse.  You can pull some of the load by re-powering the brake light through a dedicated inline fused wire from the battery side solenoid terminal to the hydraulic brake switch.  What items do you want to add?  Would they be wired hot with ignition on or hot with ign off?

Edited July 25 by greg g

[Sam Buchanan]

Theoretically.......one fuse is not as lacking on these very simple cars as it might first appear. A fault anywhere in the protected wiring should blow the fuse and protect the wiring. The problem is that a fault in an isolated location (one tail light?) could take out all the lights. Individual fuses work around this scenario. 

 

A good rule of thumb is to only replace the fuse one time. If the fault was random the new fuse might last long enough to get home, but if it blows a second time there is probably a major fault and game over until the fault is repaired.

 

As stated above, in-line fuses can be used to add more specific protection. The heater motor is a good place for an in-line fuse, just make sure it has a lower rating than the main fuse. But replacing ALL the wiring is the only way to properly install a new fuse panel, and a 12v harness is a big no-no because the wires can be too small for the greater load of a 6v system.

 

So have a good understanding of the wiring architecture before making changes, be sure new problems are not added where none existed previously.

Edited July 25 by Sam Buchanan

[Young Ed]

The tricky part is that fuse only protected the lighting circuit. My car also has an inline fuse for the radio and another for the clock. Beyond that the rest is fuseless

[Sniper]

On 7/25/2024 at 4:15 PM, Young Ed said:

The tricky part is that fuse only protected the lighting circuit. My car also has an inline fuse for the radio and another for the clock. Beyond that the rest is fuseless

 

Technically speaking, if there are no dedicated fuses then the wiring becomes the fuse.  Not a good thing,