General concepts - Automotive electrical

[Ian Tolond]

Hi Forum,
I have been reading up but cant get / find a definitive answer on this.

firstly - I understand the purpose of a fuse is to to protect a circuit (shorting fires etc..) this is all good

what I am having trouble finding/ grasping is the concept around fuses and power distribution.
A single fuse which protects a number of circuits (example only... interior lights, reverse lights, wiper washer of the same fuse)

1. Say the fuse is 15 AMP, does this equate to all the power distribution wires (in this case to 3 separate loads) add - up to 15AMP
2. or.. each of the load wires is 15 amp rated.

I assume the latter, but still looking for some insights..

Additionally anyone can point where I may get distribution header type connectors (Like OEM)- I can find the dist blocks but not much on inline header type connectors?

 

[Adam W]

It's the former - a 15A fuse will continuously allow 15A through it regardless of how many circuits are fed from it. Any more current than that and it will blow - the more current over it's rating the quicker.
This can be for two reasons - firstly that too much current is being drawn, for example from a light bulb of a wattage which is too high for the circuit that has been designed, from poor maintenance such as a motor with worn bearings, or secondly if there is a short-circuit somewhere, caused by something like worn insulation around the cable or liquid between two contacts.

 

[static zap]

Wiring damage from welding work , another favourite unexpected short ..on nice new wiring !

 

[Devonchris]

Its the latter. If all the wiring on that circuit is protected by a 15A fuse, then any wire not rated at least 15A would overheat in a fault condition before the fuse did. Presenting a possible fire risk.

I'm sure Adam W also knows this but had misread your question, which was not very clear, and its rather late.

 

[Adam W]

Just to clarify: all of the wires fed from a 15A fuse must be rated to 15A, for example if you had one light, one motor and one pump, wires going to each of these should be able to carry 15A. That way if you get a fault on any individual piece of equipment it will still be able to carry the fault current.

Thanks Chris for pointing that out - as you say the question was ambiguous, it's late, Friday night...

 

[Ian Tolond]

ok get it but to paraphrase....

single 15A fuse with feeds 3 x 15A wires.....
should any single wire (load) exceed 15A then the fuse will blow, isolating current from the source to any of the wires (loads) connected

Any insights on the header distribution connectors or do i just use molex type connectors?

 

[telectrix]

not sure on your Q about connectors. I would not use scotchlock connectors. try wagos lever type. google wago 221.

 

[Squid]

not sure on your Q about connectors. I would not use scotchlock connectors. try wagos lever type. google wago 221.

I would use solder and heat shrink, cars vibrate, have Wago's been tested using the vibration test to standard BS H1T?