I need a diagram for a craftsman solder gun model 113 540450 med dutt 140/100 watt dual heat

These were very simple and sturdy soldering guns [I still have 5 or 6 of them in various sizes] They basically have a transformer wired so that the heating part is basically a short circuit of the large low voltage secondary winding [very low voltage] and because the tip is higher resistance than the rest of the heat producing end, it gets hotter sooner. The secondary is just a single loop of the tube that holds the tip. Usually the only maintenance is to loosen and re-tighten the tip mounting nuts so that there is a good electrical connection [no connection = no heat; poor connection = poor heat]
There may be another small secondary winding that provides power to the light but I think the older ones just attached the lighting wires to the large secondary.
The primary [line voltage] winding of the transformer is switched such that the higher wattage powers the lesser resistance part of the winding and the lower wattage powers the higher resistance part of the same winding. In other words there is a single wire for the primary that has a tap near one end of the winding for dual heat.
If the two windings to the switch are mixed up the higher heat will just be at a different trigger position; if you don't like it, switch them around.

Also check the connection to the non-switched wire from the cord for a good connection. The switches are still available, at least for the newer models; do a google search for
Weller soldering gun switch
or
Weller 7324

Untitled Document [for a switch supplier]

Weller Switch Dual Heat Gun 1 Each 7324

There are a number of items you could use to cover (repair) the exposed wire. I agree the quickest repair would be to use electrical tape, everyone has it at home but I don't find it very durable. The easiest, most durable, waterproof, and coolest solution would be to use Bondic
Bondic The World First Liquid Plastic Welder Not Glue

I found it the other week at my Redmond's Home Hardware store and I keep finding things to use it on. It has a precise applicator and the flow of material is very controlled so it allows for very tidy repairs.

You could also use liquid electrical tape, it's messier but it will stick better than regular electrical tape

If it has been used a fair bit then probably just need a new tip. Can pick them up cheap enough from Maplin etc.

right here, I took you to the page its listed on http://www.newark.com/weller/7324/switch-for-dual-heat-models/dp/33F163?whydiditmatch=rel_default&matchedProduct=7324

A soldering gun is used much the same as a soldering iron for melting solder mainly to connect electronic components to circuit boards. To use it you plug it into the electricity mains and press the trigger. This causes the metal tip to heat up. Allow a minute or so for it to reach full heat and press it to the components you want to solder together. When they heat up press the solder against them. The solder melts and runs on and between them forming a bond. Remove the soldering iron and release the trigger. Once the trigger is released the gun starts to cool down again.

If you've used a soldering iron before you'll probably find the gun more awkward as it cools down every time you release the trigger. It's really only useful for quick jobs where you're not going to need it every few minutes. For other jobs where a lot of soldering is involved a soldering iron is better. The advantage the soldering gun has over the soldering iron is that it heats much faster for quick jobs.

Often the material used for eyeglass frames will NOT take solder.
If you want to try soldering you likely will need a flux that has zinc chloride. You should probably use a harder solder like StayBrite. You put some flux on the joint which needs to be held fixed while soldering. You heat the joint with the soldering tip and apply a little of the solder. One should "tin" or wet the tip before using by applying flux to the tip and melting a little solder on it. Search YouTube as someone probablly has a video on soldering.

25 watts is a pretty light iron for the kind of work you are doing, but if it works---. Tips that are just bare copper tend to erode over time (the heat causes the copper to mix with the solder and thus erode). The better tips have iron plating over the copper which protects the copper. Silver solder applied over the bare copper works in much the same way and can be applied with a propane torch. Hope this helps!

Your 8975 is rated at 120 Volts 11.6 amps and will consume approximately 1390 watts.

I can tell you that an inverter will eat your battery and put lots of strain on your charging system. I dont know what your application is, but I wouldn't rely on my car battery to run this device to defrost the window or heat the car.

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Where soldering irons have a heating element that heats a copper or alloy tip; in a soldering gun, the tip is also the heating element. Most soldering guns are hot enough to solder in less than 5 seconds and cool enough to touch in less than a minute. Soldering guns are ideal for the typical home electrical job like connecting speakers or installing automotive accessories. These jobs often have only a few connections to solder so a soldering gun can be a real time saver.