1. Damaged coil. Broken magnet wire

Damage to a single turn of magnet wire will result in failure in the pickup working. You may get a thin faint signal to the amplifier but if you turn the tone control down for the particular pickup and you have no sound, that is usually a sure sign that the coil is bad.

2. Cold solder joints

This can happen if the joint is moved or if you blow on it. Often the eyelet isn’t heated enough to melt the insulation on the magnet wire. Just re-apply heat to the solder joint if you see no signs of coil damage. On humbuckers the small hookup wire connected to the coil can have a bad or cold solder joint. The humbucker coils are more delicate to work on and extreme care has to be taken when removing the insulating tape to repair or check out if the coil is damaged. Often pulling too hard can break the magnet wire within the coil.

3. Coil damage due to removal or applied covers

Covers can be filled with dust and debris from years of playing. The debris can be connected to the outer wrappings of the coil and should be left alone when all possible. On humbuckers the connecting joint between the cover and bottom plate can often snag the bobbin and tear the coil when being removed. Make sure all the solder is removed and try using solder wick. It will get rid of excess solder between the bottom plate and cover.

4. Cold solder joints at eyelet’s

Fender and replacement pickup companies use eyelet’s pressed into the vulcanized fibre and it’s the place where two connections are made. The beginning and finish of the coil is connected there along with the beginning and finish hookup wires that connect to the control plate. Inserting the hookup wire can break the beginning or finish wire in the eyelet.

5. Broken wires at eyelet’s (beginning or finish)

I’ve seen many breaks in the magnet wire from the beginning eyelet and to where it gets covered by the outer wrappings of the coil. Repairing this can be difficult. The breaks often occur from the finish of the coil to the finish eyelet. This can be repaired much easier if care is taken to remove a turn or two that ends up being inserted into the finish eyelet.

6. Movement of magnets on single coil pickups

Magnets used on early Fender pickups can have rough pits from sandcasting when the rods are manufactured. The coil is wound directly around the rod magnets and movement can snag and break the inner wraps of the coil. If this happens the coil will have to be completely unwound or removed and rewound.

7. Magnets get demagnetized

Loss of power in pickups can be due to magnets becoming demagnetized by external sources. As long as the DC resistance is measuring properly the de-magnetized magnet can be re-magnetized and calibrated to proper strength.

8. ICPC-Inner Coil Pole Corrosion

When a rod magnet corrodes and the rust breaks down the insulation on the copper magnet wire. The breakdown of insulation and the exposed copper wire oxidizes and eventually breaks, making an open circuit.

9. Faulty connections and connections at control plate or jack

Switches and controls can eventually break, get bent or wear out. This will affect the proper working conditions of pickups. Cold solder joints can happen and re-soldering will usually do the trick. Many jacks are brass and nickel plated. The plating inside the jack can wear thin exposing the brass. In time the brass can oxidize and not make proper connections to the shaft of the plug. Using a small rod and sandpaper will help wear away the oxidation inside the jack. If consistent problems exist, the jack should be replaced.

10. Bad Cords

During my early days of playing I had a hard time finding good guitar cords. I was always repairing or buying them. I made many of them too! Make sure you check all your cables and especially the connections between your foot pedals. Check the jacks on the pedals too. Many have several terminals that are used for turning the battery power supply on when the plug is inserted. If you leave the cord plugged in the battery may be drained.