Equipment protected by the fuse block I sell/ new info, are the smaller wired circuits protected? How about the starter? Options

[Tom]

A question put to me by a member during a discussion on another thread ( and copied below) prompted several days of thoughts and questions to myself, so I put together a test circuit and tested the fuse block using 22 ga wire to see if a short circuit would cause damage to the small wire or blow the fuse.
My circuit consisted of 12 ga wire to the fuse block, then 18 ft. of 12 ga wire to the 22 ga wire and then hooked the 22ga wire to ground. Upon closing the switch, the fuse blew almost instantaneously. This was a 20 amp fuse. The wire was not even warm. To take it further, I installed a 30 amp fuse in the fuse block and retested. Same result.
So, to answer the question below, no further fuses should be necessary.
The things listed below were unfused from the factory and if you installed one of my fuse block kits, your circuits are now fuse protected. Will they always be protected? Yes they should, however, in electrical circuits anything is possible. I have seen and witnessed some unexplainable events. What made these particular circuits so bad was their being unfused from the factory and the fact that 22 gage wire has a very low amp rating, so that is where the fire would be. As soon as the 22 ga wire opened, (it in effect became a fused link) the circuit was opened and current would stop.
My test circuit had 0.14 ohms resistance, therefore as soon as the power was applied the current was in the neighborhood of 87 amps. Battery voltage of 12.2 volts, (not my car battery,a spare test batt.)
The starter motor and the alternator can be fused by adding a high amp fuse at the battery in line with the large starter wire.
Tom
EDIT:
I want to clarify something some of you may have questions about. In a properly designed electrical circuit, ( circuit defined as a source of power, equipment, the wires, switches, fuses, and connections necessary for the circuit to work) , the fuse will blow when the amperage in the circuit exceeds the rated amperage of the fuse designed into the circuit design( usually plus 10%). However, all circuits don't have the wires sized to handle the complete circuit amperage. This can become a problem when the circuit where the small wires are starts drawing excessive current. It could do this because of insulation deterioration due to age, rubbing, or our intervention ( meaning we did something to the wire's insulation). A common occurrence is disassembling something and when reinstalling it we pinch the wire between the part and ground. Sometimes a direct short, but sometimes there could be a change in resistance of the circuit at the small wire. An example: a 22 ga wire will handle around 2-3 amps ( I am finding conflicting info here, but for an example 3 amps will work). With the circuit operating normally, all is well and the part of the circuit with the 22ga wire is drawing 1.0 amps and it's resistance is 12 ohms. The circuit is protected by a 25 amp fuse and it is not being blown. We go in and remove the part that the 22 ga wire is feeding and when reinstalling it we pinch the wire and unknown to us at this time the circuit resistance has decreased to 1 ohm for that 22 ga wire. Using ohm's law ( I=v/r) we find that the current in that part of the circuit will increase to 12 amps. The fuse is not overloaded and will not blow, but the wire will not handle 12 amps so it overheats and eventually shorts directly to ground, blowing the fuse.
Here is how to prevent things like this happening, or at least minimizing them. When you are going to be removing and working on electrical equipment, always disconnect the positive battery cable. ( I always remove the neg also first, that way if my wrench contacts the body of the car when disconnecting the positive I don't get a welding lesson.) Now temporarily rehook up the negative battery cable, turn on what ever you will be working on, and take an ohmmeter reading between the positive battery cable and ground. This is the circuit resistance of the circuit you are working on plus what ever else is also in parallel. After you have completed the work, take another reading to ensure the second reading is not significantly lower that the first one. If it is, time to double check your work. If not, rehook up the positive and negative battery cables, but leave the positive one loose enough to take off by hand in case anything goes wrong.
Hope this is of some help, I know it was kind of long, but I am trying to get the info to some whose electrical understanding is in progress.
Tom

What other fuses do we need Tom and can you make them for us?

Ignition switch
Main power relay
FI ECU
Starter motor
Alternator
Headlamp switch
Fog lamp indicator bulb
Seat belt warning buzzer
Fasten seatbelt bulb

[JeffBowlsby]

I appreciate what you are doing with the fuses Tom, you have great insight on the weaknesses of our cars. A few of the wires to the headlight switch are 24 gage, will that affect your testing/fuse selection?

[Tom]

Jeff,
I don't think so. There is little difference between amp ratings for 22 ga. versus 24 ga. when compared to the high currents when a direct short happens. The instantaneous high current delivered upon a short to ground of any wire that is B+ is so high that the fuse blows before any heat can build up in the wire. I searched several web sites for 0.5mm to std awg and some were 22, others 24. All I had on hand was 22.
Tom

[bandjoey]

Knowing little about electricity except that it hurts when applied to the tounge and other parts.....

Lord let me be Witness to Tom's invention.

Shorted the yellow starter wire directly to ground, and POP the fuse blew immediately..Thank Goodness.

I was just dubmb enough to install another fuse and POP let it blow again before I started to look for the problem. (IMG:style_emoticons/default/headbang.gif)

Plugged the yellow wire properly into the starter and WALAH, no more problems.

(IMG:style_emoticons/default/piratenanner.gif)

[Tom]

Bill,
I am so glad to hear something positive like this happening. Not that it happened, but the fuse block you installed did it's job of protecting your car's electrical system! (IMG:style_emoticons/default/piratenanner.gif)
I joined this 914 site late and always appreciated the great work done by Jeff and wondered a long time how I could contribute without stepping on his toes for what he has done. I am so pleased I have been able to do something to help our members car's electrical systems survive into the future. thank you for posting this.
Tom, feeling good for you and your car's electrical system!!

[Mike Bellis]

I totally agree with your product.

The biggest danger with unfused copper is heat transfer. The copper will "light up" like a heater element. Glow red and melt anything around it. If you get lucky, the wire melts and breaks, thus stopping the short.

Even the VW Corrado, Jetta, GTI, etc had unfused wires to the radio. Short the "keyed switch" wire to ground on these models and you will have to replace the ignition switch. Just not before you drill out the shear bolts.

I disagree with a 24 gauge wire installed in a 914. 24 gauge is the size of a single CAT 5 phone conductor. I do not know of any that small in a 914. The smallest I've seen is close to 18awg. The high beam wire in the column may be as small as 20awg, but I don't think so. Hard to tell as the older Euro wire is in mm and not awg.

[Tom]

Adding the info on this battery terminal. Looks like a great idea, but a little pricey at about the $30.00 range.?
I am thinking of getting one to see how it looks and if I can use it with my fuse block. Would like to get the second one, but it is no longer available.
Tom

Edit: StreetWires BC2PF Fused Battery Clamp (+) AFS large pic.

[Mike Bellis]

Adding the info on this battery terminal. Looks like a great idea, but a little pricey at about the $30.00 range.?
I am thinking of getting one to see how it looks and if I can use it with my fuse block. Would like to get the second one, but it is no longer available.
Tom

Edit: StreetWires BC2PF Fused Battery Clamp (+) AFS large pic.

That looks like a great product idea.

I have a fuse too. Mine is wired battery terminal - to - fuse - to -disconnect switch - to - starter. From the starter I have a cable to a main power relay and EFI fuse panel (mounted in the trunk). I am running 1/0 welding cable as the battery lead. My battery is in the front trunk.

[Tom]

Mike,
Thanks for the info. I am going to look at your build thread to see if I can find a pic.
Tom
Edit: Found it, very nice work Mike. Beyond what most would even consider. Love the bulkhead connector!!