Modified five wire upgrade

Some time ago, alternate approaches were applied to Athearn blue box engines to get rid of the metal strap that connects the top of the motor with the truck towers.

Over time, the strap looses and tends to rust. Both of these lead to erratic operation of the engine.
The most popular of these approaches is the so call “5 wire” method. As shown in the schematic below.
(This sketch was used in the NMRA description of the tuneup of Athear locos.)

Basically, the strap is removed and wires are soldered directly from the truck towers to the clip on top of the motor. Additionally. a wire is soldered to the bottom motor clip and connected to the chassis by putting a screw in an obscure location. This required a hole be drilled and tapped in the chassis. More often than not this last step was not done, likely because of the requirement to drill and tap a hole. The metal strap could be eliminated with only the first step.

Additionally a wire was soldered from the light to the top of the motor and the other side was connected to the screw. Like the second step, this was often not done. One side may have been connected to the top of the motor, but the stock chassis connection for the light continued to be used.

Even when the full method was utilized, several blue box loco issues were not addressed. These are:

1. The old motor mounts were made of a rubbery material. These were not very robust.


They usually did not survive a motor removal. Even if they were not disturbed, they did not hold the motor in place very well and they would become brittle over time. Eventually they would crack and become useless as a mount. These mounts were used to hold the bottom clip against the chassis. This was a critical electrical connection point, which would fail with the mounts. The wire from the motor bottom clip to the chassis would solve the electrical connection problem. However, the loose motor would lead to all sorts of problems.

2. The electrical path from the truck to the chassis was accomplished by gravity and two metal surfaces that are in contact with each other. These surfaces need to be perfect parallel planes because they rotate against each other.

Unfortunately, they usually did not start out as parallel planes. Also over time rust or grit would minimize the contact surface, as shown. Eventually the connection was so poor that the engine performance was impacted.

Proto 2000 and Atlas dealt with this by wiring the truck directly with the motor. Thus electrical power was no longer dependent on the condition of these two planes. Atlas also took care of the motor mount issue by holding the motor in place with screw mounts.

With the needs of DCC, enhanced versions of the five wire method came on the scene. For some time now, I have been using what I call a “modified five wire” technique. I normally stop short of going to DCC, but the DC system can be easily converted to DCC as required.

This technique is not unique to me, but this is how I do it:

1. The wire colors that I use are consistent with the NMRA DCC standard. The right track rail wires are red, the left rail wires are black. The wire to the top of the motor is orange and the bottom motor clip wire is grey. The lite wire colors are blue and white. (At this time I’m actually not showing the lite wire installation.)

2. The motor is isolated from the frame. As others do, I use a piece of non conductive tape between the motor and the chassis. The motor clips are reversed, so the bottom clip with the connection legs is on the top.

3. The motor is mounted to the frame using Athearn’s latest screw mounts that are used in later vintage engines.

4. The red wires are soldered to the right side of each truck and the black wires are soldered to the left side of each truck.


5. After the trucks are installed, the red wires are soldered to the orange wire and the black wires are soldered to the grey wire.

6. The lite wires are properly connected to the light and the blue is connected to the red-orange connection and the white is connected to the black-grey connection. (Not shown)

7. The wires are then properly secured with electrical tape.
Care needs to be taken to be sure the wires do not interfer with the frame. Sometimes that requires longer wires that are fed up on the loco end side of each truck tower.

This approach yields the benefits of the 5 wire approach as well as the appropriate Atlas and Proto 2000 techniques.

The beauty of thus approach us that a decoder and be installed with a minimum effort.

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