The Ghost That Preached Electrification: A Deep Dive into the Renault DF104 “New”
By: [Auto Historian]
In the pantheon of automotive “what-ifs,” few vehicles are as simultaneously obscure and prophetic as the Renault DF104. To the casual enthusiast, the name means nothing. To the electric vehicle historian, it is a Rosetta Stone. But when you append the word “New” to it—the Renault DF104 New—you unlock a strange, layered story of oil shocks, French industrial stubbornness, and a vehicle that was technically brilliant but commercially stillborn.
This is the story of the car that should have launched the EV revolution two decades before the Nissan Leaf and 30 years before the Tesla Roadster.
1. New Old Stock (NOS)
Occasionally, a barn find emerges. These are crated, never-assembled tractors or original parts left over from the Le Mans factory. A true NOS DF104 (0 hours, original grease, original tires) is the holy grail. When one surfaces at auction (like Agritechnica or Retromobile), it can fetch upwards of €40,000–€60,000—more than a brand-new compact tractor.
Step 1: Visual Inspection
- Check the main fuse box for water damage or green corrosion.
- Inspect the wiring loom for visible breaks or chew marks.
4. Potential Causes
The causes are generally electrical. They are ranked from most common to least common:
A. Wiring Harness Issues (Most Common)
- Corrosion: Water ingress into the main fuse box (often located near the battery or under the dashboard) corrodes the CAN bus pins.
- Rodent Damage: Squirrels or rats chewing through the wiring insulation, severing the CAN High or CAN Low wires.
- Broken Wires: Fatigue in the wiring loom, specifically where the harness bends near the trunk hinges (hatchbacks) or near the steering column.
B. Connector Problems
- Loose or unplugged connectors on major ECUs (Engine ECU, ABS pump, UCH).
- "Tin whiskers" or oxidation inside multi-plugs.
C. Faulty Control Units
- If one ECU (e.g., the ABS module or the Instrument Panel) fails internally, it can "short" the CAN network, preventing all other modules from communicating. This drags the whole network down.
Step 2: Check Resistance (CAN Bus Health)
- Locate the 120-ohm termination resistors. These are usually located inside the Engine ECU and the Instrument Cluster (or UCH).
- With the battery disconnected, measure resistance between the CAN High and CAN Low pins at the diagnostic port (OBD pin 6 and pin 14).
- Good Reading: 60 Ohms (Two 120-ohm resistors in parallel).
- Bad Reading: 120 Ohms (One resistor missing/broken wire) or 0 Ohms (Short circuit).
The Powertrain Revolution
The original DF104 used a rudimentary DC series-wound motor. The DF104 New upgraded to a separately excited DC motor with a thyristor (SCR) chopper controller. This was space-age tech in 1975. The chopper allowed the motor to draw power in pulses, drastically reducing energy loss as heat. Efficiency jumped from 45% in the original to nearly 78% in the "New."
- Motor: SAFT 6.5 kW continuous (16 kW peak)
- Battery: Nickel-Zinc (Ni-Zn), 72V, 100 Ah
- Weight: 1,120 kg (2,469 lbs) – heavier than a Mini, but the battery alone weighed 350 kg.
Part 5: Technical Deep Dive – The DF104 "New" Spec Sheet
If you are commissioning a "new" build, what should the specification look like?
- Engine: MWM D327-3. Bored to 98mm if necessary. New injectors (Bosch style) and a recalibrated injection pump to run on modern low-sulfur diesel (add a lubricity additive).
- Transmission: The infamous "Renault 3-speed" with shuttle. New synchro rings are available. Convert to a hydraulic shuttle if doing a restomod.
- Hydraulics: 25 liters per minute. Upgrade the original single-acting valve to a dual-acting spool valve for modern hydraulic top-links.
- Tires: The correct look is 13.6R28 rear and 7.5R18 front. "New" means using Alliance or BKT tires that replicate the old Michelin tread pattern, not modern radial ag tires.
- Electrics: Convert to 12-volt negative ground (original was 12v positive). Install a hidden kill switch and an alternator upgrade (55A).
Where to find a "New" DF104
If you want one, do not call your local Renault dealer. They will laugh.
- Specialists: Look to Classic Autos Engineering (UK) or D. Fermaud (France), who are currently casting new aluminum blocks based on the DF104 blueprint.
- Price: A complete, race-ready "new" DF104 engine starts at €12,000. A full restoration with NOS parts? Closer to €25,000.
- Lead time: 6 to 9 months. Every engine is hand-built.