The Heljan Di3 was introduced in 2000 and for a while it only HO Di3 locomotive that has been produced in era IV versions. Roco makes a Di3 but so far only produced era III versions. In the mean time NMJ has started to produce later era models as well.

The Heljan Di3 is a very nice model and captures the beauty of the NOHAB very well. Unfortunately the driving characteristics suffer over time a little bit. The wheels are capturing dirt very well and that impacts the conductivity of the wheels. Frequent cleaning is needed and that is a nuisance. Solutions for this have been discussed on forums and one solution is to replace the wheels with Hobbytrade Di4 wheels.

I started to look at alternative solutions and tried four different solutions that I will described on this page:

• Put Heljan Di3 shell on a Roco NOHAB frame
• Polish the Heljan wheels
• Replace Heljan wheels with Roco NOHAB wheels
• Replace Heljan wheels with Hobbytrade Di4 wheels
• DCC powerpack solution

These pictures show the shell of a Heljan Di3.619 on the frame of a Roco Di3 (cat no 62950). It pretty much fits without much adjustments. Only the light fixture in the Heljan shell needs to be removed as it is too big. Only the lenses remain. This modification results in a very nice running locomotive.

I didn't pursue this experiment beyond what is shown in the pictures. The extra Di3.619 that was used for this experiment was later renumbered to the Di3.602 (with GM logo).

The Heljan wheels have a brown color that makes them look authentic but as mentioned before it picks up dirt very fast. On this locomotive the wheels were polished with a dremel tool to remove the top layer of the wheels. This makes it less susceptible to dirt pickup.

This model has its Heljan driving wheels replaced with Roco wheels. Nothing is visible from the side. The picture from underneath show silver nickel wheels on the outer sides of each truck.
This model is special because it has a sound decoder, the speaker is visible in the dieseltank. This modification was done by Bergen Modelljernbane.

To the left you see two Heljan trucks, the left truck has Roco wheels, the right truck the original Heljan wheels. To fit a Roco wheel set you have to remove the Roco gear from the wheel set and replace it with the original Heljan gear. The Roco wheels don't fit exactly because of the double isolation, so a little material has to be removed from the truck.

This model has its wheels replaced with Hobbytrade Di4/ME wheels. Similar to the Roco wheels replacement the Hobbytrade wheels have more a nickel silver look.
Also this model is modified by Bergen Modelljernbane, it has the top light removed from the nose (only on cab 1).

To the left the Heljan truck with the original wheels. To the right you see the new wheels installed, except for the center axle, so you can see the color difference.

With DCC powerpacks it is easy to solve any short-term power pickup issues. In one of my latest installs, I installed an ESU powerpack and an ESU Loksound 5 decoder in an Heljan Di3. This solved the power issue.