Things wear out, stuff gets dirty, light bulbs blow.  Fortunately, Z-Scale locomotives are meant to be repaired and they all have things in common. Let’s look at a basic Märklin locomotive and do routine maintenance. You will need a few tools for this task, along with a repair part or two.  The tools:

• Screwdrivers - Small ones; most repairs use straight blade screws, but there are also some cross-point screws used.
• Tweezers - a nice pair with pointed ends.
• Vision Enhancer - Well, you might not need one, but a magnifier like the Opti-Visor helps greatly.
• Oil - Märklin offers an oil, but if you do not have it, use only light model train oil that is plastic-compatible.  No WD-40, no salad oil, no automobile oil, no grease, NO GRAPHITE.

That said, you need a clear workspace with some sort of protective cloth over the work surface.  Keep in mind that you will be encountering oil residue and carbon residue from the motor brushes. And errant parts may fly off of your work surface.

So, here it is:

Your first task is to remove the locomotive superstructure. With most of the electrics and diesels, it is a matter of gently prying the sides of the locomotive shell outward and letting the mechanism itself drop downward.  Many of the steam locomotives have one screw on the top of the engine.

Once the locomotive is open, you may need to do some minor disassembly. Keep in mind that a human being assembled this engine originally, so it can be reassembled by you.  Keep in mind that the person who originally assembled this engine may also have had special assembly jigs to hold everything properly while the engine is being fitted together. This is especially true of almost all of the steam locomotives and a few of the electrics.  The Swiss Crocodile, in particular, can be nasty to reassemble. So, don’t get in over your head. In most cases, you should be able to do motor brush changes and oiling without taking the locomotive completely apart.

One helpful location is the Märklin, Inc. web site. There are downloads available here for the maintenance manual and spare parts book, here.  Most locomotives have a technical sheet:

First, identify the general components:

The motor brushes are copper with bits of shaped carbon attached.  The carbon presses against the motor armature; electricity is conducted by the copper from the motor circuit board on the top of the mechanism to the armature.  With use, this area of the motor will be sooty and possibly oily.  When the carbon wears out, the motor cannot get electricity and will not run, or will run erratically.

The motor (12) has a rotating armature inside which is a series of wire windings.  There is a magnet on the outside of the motor, and as current is progressively passed through the “poles” of the armature, the armature starts to turn.  In turning, a new set of windings is activated by electricity flowing through it.  The motor spins faster as the voltage increases.  There are bearing points that hold the armature in place in the motor, adjacent to these bearing points are two gears, one at each end of the motor. You should lightly oil these bearing points, trying to not get oil on the armature. The small disk with wires on top of the motor is a capacitor which helps prevent TV and radio interference.  The two motor gears mesh with the drive train gears:

The gear & worm assembly (14) has a large gear at one end and a worm gear at the other end of a steel shaft. This shaft also has two bearings which fit into the frame of the locomotive. When disassembled, these will slide back and forth along the shaft. Exercise care when replacing the gear & worm assembly, insuring that the two bearings are properly seated. This locomotive has two gear & worm assemblies, and oil should be lightly applied at all the bearing points and on the gears. The worm gear then meshes with the trucks of the locomotive:

The body of the locomotive truck (15) is cast metal; a plastic side frame (23) holds the wheels in place. Under normal circumstances, you probably do not need to disassemble the trucks, but they can be removed from the locomotive frame.  Note the two oval slots in the locomotive frame. A steel shaft (18) holds the truck to the frame; it fits through a large gear at the top of the truck.  The oval slot allows the truck to pivot, letting the locomotive go around curves. On top of the truck assembly, you will see two phosphor bronze “fingers”.  Take great care to not bend these pieces.  The fingers conduct electricity from the wheels up into the motor. If you encounter erratic operation, in many cases it is because the wheels of the locomotive are dirty, or these conducting fingers have become bent or are dirty.  As with the rest of the locomotive, a light oiling of the gears and shafts will be helpful.  Try to avoid giving a light oiling of the electricity conducting parts such as the pickups. Also, avoid getting oil on the coupler spring (21).

Another important matter involves keeping the wheels clean. Because the locomotive emits oil and carbon from the motor brushes, and the locomotive operates in the real world, you will find deposits of dirt and crud on the wheels. This may include pet hair, carpet nap and other foreign debris.  This stuff is nonconductive and eventually the locomotive will stop running because of the accumulation.

There are a couple ways to deal with it.  You can use a toothpick to manually clear off the deposits.  Ken Brzenk, of Märklin, Inc., has suggested making a simple device to correct this. Take two straight pins, solder a brown wire to one, and a red wire to the other, then connect the wires to the transformer.  Turn the locomotive upside down, propping it so that it cannot shift around.  Turn the voltage on and put one straight pin on one wheel, and the other pin on a wheel on the opposite side of the locomotive. The locomotive starts running, and the points of the straight pins clean off the deposits.

If you do not feel confident in maintaining your locomotives, your dealer should be able to offer you assistance. There also is a group of authorized Märklin service centers around the country which are qualified to perform repairs on Märklin trains.  These dealers are required to maintain an adequate inventory of parts and tools which make speedy repair possible. Also, the repair centers have handled many of the problems that you may encounter, and Märklin’s technical manuals are quite explicit and detailed. Don't feel too self-conscious if you are bringing your locomotive to the repair center in pieces. I guarantee that you are not the first person to have done so.