<VV> Re: Measure Voltage Drop (main fuse question)

[JVHRoberts at aol.com]

Not to sound horribly argumentative, but you ALL know how anal I am about 
headlight wiring, and voltage drop. It's amazing how much there is, and where you 
find it. Remember circuit breakers and fuses blow or trip by getting hot, and 
that means RESISTANCE! I've measured it across fuses and breakers, and at or 
near their current rating, and the voltage drop is often more than a volt! 
So, I hear ya on older cars, questionable wiring, etc., that a bit of 
protection isn't a bad idea. With that in mind, I've found the MAXI fuses to have the 
lowest voltage drop. 
On the other hand, on two of my cars where I have KILLER headlights, I left 
the big fat wire to the relay banks unfused, and ran it inside a piece of 
rubber hose, to prevent it from shorting to anything. Then I have an ATO fuse for 
each filament. The total voltage drop, in this case, is 0.25 volts from the 
battery to the bulbs. 


In a message dated 2/24/2005 7:38:15 PM Eastern Standard Time, NicolCS writes:
II doubt that you will see even a tenth of a volt at full current and I feel 
that we do need protection.  In fact, I'll go and check the voltage drop at 
Imax on my '66 and report back.  Why add one?  Our cars were built to provide 5 
years of service, give or take and we (like B-52s) are at many multiples of 
the design-life.  Things wear, chafe, and degrade and we have (in most all 
Corvairs) unfused B+ running all over the car.  Poor repairs (on a Corvair??), 
corrosion, and shoddy parts lurk. Most people don't have a clue as to how to 
repair or modify wiring properly.  Why not protect the investment with a $15 mod?  
Many customers have brought in expensive cars that nearly met their demise 
through wiring fires.  Also, insurance companies sometimes view a wiring fire as 
"poor maintenance" and will deny loss claims. So, every car that gets wiring 
repair in my shop gets a Maxifuse.  I don't see any significant downside.  
Manufacturers have been fusing the B+ for over 35 years.
IMHO, Craig (screw loose, but good fuse) Nicol

<snip>A few tenths on a 12v system is more than I'd like to see, especially 
since 
incandescent bulbs, like the headlights, have a brightness proportional to 
the 
3.5 power of the voltage. 
So, the real question is, why add something that does this, and you don't 
need?<unsnip>