Headlight Wiring

[soybean]

No, not what you are thinking, another one. This is new.
I am in the process of rewiring the front end of my car. One of the previous owners had rewired the headlights using 10 gauge wire, a little overkill, but still good. In this endeavor I purchased relay kits from Mad electrical, http://www.madelectrical.com/index.shtml , to keep from burning the fuse box up. The kits come with 12 gauge wire and have an 18 gauge fusible link wire. Will I lose voltage to the lights going from 10 gauge, to 12 gauge, to 18 gauge (fusible link), or is this a moot point? I am as lost in wiring as in metric sizes of bolts. Thanks, Jarrell

[namba209 (R.I.P.)]

Jarrell, I'm not sure what size the original fuseable links are on the Opel, although there are only 3 for the whole system. Going from 10 to 12 gauge wire for the headlights isn't too bad, the original wires were 12G. As far as using 18G for a fuseable link, I don't know, it depends on how long it is and the resistance to current flow. I know on some circuits I've seen wires the size of cat's whickers have been used for fairly high current flow but they were very short. I would be sure the fuseable link can carry the current of both headlights on hi-beam and put the link somewhere easy to get at in case it does burn out. And isolate it from the rest of the harness too. JMTCW

[nobody]

Ok to start at the beginning the wires you would have had originally were a 2.0mm squared. The Germans and a few other countries have been doing metric wire for a very long time. With that said a 12 guage wire is a bit bigger than a 2.0 and a 14 guage is more like a 1.5. Most if the Opel wiring was done with 1.0 and the lights are 2.0 with a few power curcuits being in the 3 and 4 range. so to answer your question the 12 is fine but I'm not real sure about the small fusable link. Given the design of them they are rated to the known use so it should be ok. I'm kind of the opposite can look at a metric wire or nut and size it but have to get out charts for the American stuff.

[Travis]

The 18 gauge wire will be so short that you'll never notice it....

-Travis

[soybean]

I was going to run from the alternator to a terminal block, with a fusible link inline. From there to battery, from terminal block, all the high current feeds. Relays for high/low beams, electric fan and foglights. The fusible link that came in the kit is apx 6" long. Thanks, Jarrell

[soybean]

It was pointed out to me later, that if you run the circuits like I had originally proposed, the fusible link from the alternator to the terminal block will carry the entire load to include the battery's draw when it is low. The advice was to feed the battery and terminal block in parallel and put the fusible links between the terminal block and the load, i.e. lights, fan, fog lights. If you did it the way I said, either the fusible link will burn out when I have max load, or if it is large enough to handle the entire load, it won't burn out soon enough to prevent damage, if say the electric fan shorts out and the head lights and fog lights are not on. Have to give credit where, where credit is due. Thanks for the tip Brian. Jarrell

[jlthunder]

I have a question for the electrical engineers out there.

Can I replace the Fusable links with inline 30 amp fuses? They would replace the fusable links on the alternator(stock), voltage regulator, and starter.

The logic is if there is an electrial problem, the fuse is much easier to replace than the link.

[namba209 (R.I.P.)]

Well, you'd probably be replacing fuses a lot, considering the stock alternator puts out 45 amps and the starter pulls a lot more than that, but the solenoid wire is less and maybe alriight for a fuse there. HTH.

[jlthunder]

Well here is my problem. The fuseable link at the alt. does not exist. Is there a stock replacement or should I contact Gil at OGTS? The other ones are still there.

[soybean]

I'm sure someone will correct me if I'm wrong, but a fusible link is two wire gauges smaller than the wire it is hooked to. Thus, a 20 gauge wire would have a 18 gauge wire, as a fusible link, soldered to it allowing the 18 gauge wire to meltdown before the 20 would be damaged. HTH, Jarrell

[bq97]

Jarrell pretty much hit the nail on the head. Fusible links are used to protect higher current circuits, generally 30 amps or more, which is somewhat higher than that of standard fuses. Today higher rated fuses are available so fusible links are not as common as they once were. Fusible links do have a few advantages over fuses. One is they are cheaper to use because there is no need for a fuse and fuse holder. This is a major plus in mass production were the bottom line matters. Another, is they are not susceptible to vibration which can sometimes damage fuses. I'm sure we have all looked at a typical inline glass fuse and it looked okay but did not pass a continuity check. The probable cause is the fuse element separated from the end cap.

Fusible links are harder to replace then fuses but there are some quick and easy methods to make them easier to replace. One method is to use connecters to connect in the smaller gage wire. This makes repairs a snap.

Something to consider when making or replacing a fusible link is the length. As stated in an earlier post the longer the wire the greater it's resistance, therefore the less current carrying capacity. Also, since it's the links job to fail put it in an easily accessible location and make sure the insulation is fire resistant. You don't want the link to fail and start a fire. Also make sure that if the link fails the ends of the protected wiring don’t contact a grounding point.

A no math method of determining what size link to use is to keep reducing the wire gage until it blows under full load and then go up 1 gage size at the same length. BE CAREFUL THAT YOU DON”T BURN OR SHOCK YOURSELF OR CAUSE ANY SECONDARY DAMAGE!

A quick and easy way to add a fusible link into new wiring is to reduce a section of the wires gage. That's what I did when I rewired my GT. It sounds difficult but with practice it's really easy to do. Take a few pieces of appropriate sized heat shrink tubing and slip them on the wire before you terminate the ends. Then select a location in the wire to make the fusible link. Neatly cut the insulation away at both ends of where you want the link being careful not to cut any of the wire strands, but if you do don't panic. Untwist the wire slightly to expose the strands. Now cut out the individual strands until you reach the desired gage. If you cut any strands while exposing them make sure they are the ones you remove or your fusible link will be reduced in size. Make sure the cut ends of the wire won't poke thru the heat shrink tubing when it shrinks. Give the wire a little twist to reset the strands, cover it with the heat shrink and shrink the tubing down. I generally use two or three layers of heat shrink depending on the tubing it's self and the wire gage. Once done it looks pretty clean and you don't have a big lump in the wire from the solder connections.

One thing to mention is that fuses, fusible links, fuse elements all serve the same basic function and that is to interrupt current flow and protect the circuit from damage.

hth
Brian

[opelbits]

A couple of thoughts to throw into this topic...

You can now get inline fuse holders that use the blade type fuses. This does two things, makes changing fuses very easy, and also increases the number of different fuse ratings and the practical availability of replacement fuses (try finding the correct glass fuse or the older red or white fuses at 9pm on Sunday night). You can also get the blade type with a little LED that goes on when the fuse blows.

The other thing I wanted to mention, German wiring tends to have more individual strands than your usual off the shelf bulk wiring you get in the US. This is beneficial for several reasons. One has to do with current flow/resistance/or something someone else could explain better than I and it also allows more flexibility in the wire which helps it deal with flexing, vibration, and of course, the rotating wire loom that feeds the headlights.

The headlight wires were originally covered in a softer, more flexible material, too, so the wires could deal with the twisting.

[bq97]

Stranded wire is constructed using different stranding sizes. Take for example a 20 gage stranded wire. It can be constructed with 7 strands of 28 gage wire, 10 strands of 30 gage wire, 26 strands of 34 gage wire, and the list goes on. Larger wires sizes are expressed using the stranding size instead of the AWG number, in other words 7/0 wire is made up from 7 strands of 0 gage wire. Just like bolts some strandings are common, some are not so common. Just like SAE and metric fastners there are common stranding sizes in standard and metric wiring so a blanket statement like "German wire has more strands" is not quite true. However, the common run of the mill wire down at the auto parts store will generally have less strands of thicker wire. Like anything else the more strands the higher the price relative to a wire of the same gage but with a coarser stranding. Stranded wire is also slightly larger than the solid wire of the same gage. Finer stranding can reduce the added bulk of stranding. This is one advantage solid wire has over stranded wire, a larger current carrying capacity in a smaller area. The cross-section area of a stranded wire is equivalent to that of a solid wire of the same gage. When you look at a 20 gage stranded and 20 gage solid wire the stranded will look slightly larger in diameter but has the exact same cross-section area or circular mill size of conductive material as the solid wire. Provided the insulation on both is the same type. Solid wire is cheaper to make up to a certian size, but is not as flexible nor as resistant to vibrations as stranded wire. That's why solid wire is used in buildings. Where flexibility is needed stranded wire is the way to go. The resistance ratings between solid and stranded wire are for our purposes the same. It's only at higher frequencies that stranded wire has a lower impedance rating because higher frequencies tend to travel on the outside edges of the conductors so the more outside edges the less resistance. This is due to the electromagnetic flux density at the center of the conductor.

A lot of useless info but if you want a more flexible wire get a wire with finer stranding.

brian

[jordan]

I bought 3 spools of wire tonight but I don't think that it is right. it is "superior Essex THHN stranded MTW 10 awg 600v wiring" it seems like it meets the criteria, but it isn't very flexable and easily has memory after a bend. Is it the right wire after all?

[bq97]

THHN wire is standard PVC coated commercial/industrial building wire for use in fixture raceways, metallic conduit and tubing. The MTW code indicates it also code acceptable in machinery, MTW = Machine Tool Wire. The conductor temp rating of THHN wire is only about 60 degrees C. Even though it has the MTW rating it is not vibration resistant and as you have found out not very flexible since it was designed for use in raceways and conduit. It will work but it’s not the best thing to use. The Essex THHN stranded MTW 10 awg 600v wire, Essex being the brand name, is probably a 19 strands wire meaning that it is made up from 19 strands of 22-gage wire. The max amp rating is 30 amps for this type of wire.

What you really should be using is wire specifically for automotive applications. Look for wire that has a designation code of SAE J1128-XXX. The Xs indicate the sheathing type.

There are basically four types of sheathings for automotive wire GPT, SXL, GXL, and TXL. GPT is PVC coated and good for about 80 degrees C. The other three are all cross-linked poly coated and good for 125 degrees C. The differences in the three poly coatings are the thickness of the coating, SXL is standard, GXL is thin walled, and TXL is extra thin walled. This also roughly equates to stiffness or flexibility within the same gage.

hth
Brian

[jordan]

Are these wire types available at napa's or autozone's?

[bq97]

They should be but I can't say for sure as I have never bought wire from an auto parts store. There is an electronics supply store close to me so I get everything I need there.

Brian

[hrcollinsjr]

I substituted an inline fuse years ago for the fusible link. Genius that I am I used a 35 amp fuse from the alternator after all that was the output, right. Well when the alternator was charging full charge it didn't blow the fuse but it did melt the solder in the fuse. It screwed up the inline holder making it difficult to get apart and to replace the fuse. Solution - circuit breaker with a higher amperage. Never had any more problems.

Harold

[jordan]

I bought some 14 guage mtw very flexable and all contained in a waterproof gasoline resistant outer sheathing with internal wire separators. As I said the wire is very flexable though it is 14 guage, will this be a problem becuase it is a smaller awg?

[nobody]

Best I can remember the Opels were German made and US guaged wire wasn't imported there for them to use. Headlights were 2.0 honest to god. If you want a good replacement

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