Complete 1968 Dodge Dart Electrical System Wiring Schematic Guide

Begin by locating the chassis wiring harness connector under the driver’s side dashboard–this is the primary junction for most circuits. The main loom splits into three critical branches: ignition, lighting, and instrumentation. Each branch uses color-coded wires; red with a blue stripe handles the voltage regulator feed, while solid green controls the headlight high beams. Verify these against the factory service manual’s color key before splicing or replacing sections.

For auxiliary systems like the turn signals or backup lights, inspect the rear harness near the tail panel. The left rear axle bracket often rubs against the loom, causing shorts–reinforce this area with protective loom tape. If the instrument cluster flickers or fails, focus on the brown wire cluster behind the gauge housing; this carries the grounding circuit. Clean oxidation from all bullet connectors to restore conductivity.

Replace brittle wire segments with modern cross-linked polyethylene cables–they resist heat and vibration better than original PVC insulation. Match gauge sizes precisely: 18 AWG for lighting circuits, 14 AWG for high-demand loads like the ignition coil. Avoid solderless connectors; instead, use rosin-core solder and heat-shrink tubing for permanent repairs. Label each reconnected wire with its function and destination to simplify future diagnostics.

Test circuits systematically using a multimeter set to continuity mode. Probe from the fuse block to the end device, noting voltage drops exceeding 0.5V–this indicates corrosion or loose terminals. For intermittent issues, flex wires manually while monitoring the meter; brittle insulation often cracks internally, requiring full trace replacement. Prioritize safety: disconnect the battery before working on the charging system.

Restoring Your Classic’s Electrical System: A Hands-On Approach

Start by locating the main fuse block under the dashboard near the steering column–it’s the nerve center for circuit protection. Each fuse corresponds to a labeled slot (e.g., “Headlights,” “Ignition,” “Gauges”), but the embossed text fades over time. Use a multimeter set to continuity mode to verify connectivity; a dead circuit often points to a blown fuse or corroded connector. Replace suspect fuses with the exact amp rating–20 amps for headlights, 10 amps for turn signals–to avoid overheating. If the multimeter shows resistance, clean the fuse terminals with a wire brush and dielectric grease before reinstalling.

Trace the harness from the fuse box to the rear tail lamp assembly, following the factory routing path along the driver’s side rocker panel. The original cloth-wrapped loom is prone to cracking; if insulation flakes off, wrap exposed sections with 3M Super 33+ electrical tape–vinyl won’t adhere long-term. At the junction where wires split to the fuel sender and brake lights, check for voltage drops: probe the purple wire (sender) and green wire (brake) with the ignition on; readings below 11.5V indicate a grounded circuit. Strip back the insulation ¼ inch, crimp a new butt connector, and solder for longevity.

For the instrument cluster, remove the bezel by prying loose the four plastic clips–force can crack the lens. The speedometer and fuel gauge share a common ground (black wire with yellow stripe) at the firewall grommet; verify this connection with a test light. If gauges fluctuate, suspect a failing voltage regulator mounted on the firewall. Swap it with a solid-state replacement (e.g., Painless Performance 30305), which eliminates the brittle mechanical contacts of the original. Reassemble the cluster, ensuring the printed circuit board sits flush; misalignment causes intermittent readings.

Finding the Right Electrical Schematic for Your Classic 1968 Dodge Variant

Begin by identifying your specific trim level–GTS, GT, or base model–as each version has distinct circuitry for lighting, ignition, and accessory systems. Factory service manuals from Chrysler’s official publications remain the most reliable source, particularly the “Service Manual Passenger Cars” series released that production year. These documents include exact pinouts for the instrument cluster, charging system, and fuse block arrangements, which aftermarket guides often omit.

For unrestored originals, inspect the vehicle’s firewall-mounted data plate. The body code (e.g., “PL” or “PM”) corresponds to wiring variations tied to regional assembly plants. Shelbyville-built units, for example, may feature altered steering column harness routing compared to Detroit-sourced cars. Cross-reference this code with the “Body Builder’s Layout” supplement available through the Chrysler Tech Authority archive, which details chassis-specific configurations.

Key Resources for Schematic Verification

• Microfiche collections: Held by the Antique Automobile Club of America library; contains original engineering drawings with edits from the design phase, useful for tracing mid-year revisions.
• Dealer bulletins: “Service News” issues from late 1967 outline last-minute circuit modifications for heater blower relays and turn signal flashers–critical for vehicles equipped with optional air conditioning.
• Harness manufacturers: Companies like Painless Performance or American Autowire sell reproduction bundles with annotated schematics that highlight discrepancies between their kits and OEM layouts.

Pay close attention to ground locations–especially near the battery tray and rear axle shocks–where corrosion can mimic wiring failures. Original schematics mark these with numbered tags (e.g., “G-102”), but reprints occasionally mislabel them. A multimeter set to continuity mode will confirm paths; expect resistance values below 0.5 ohms between the engine block and negative terminal clip for intact connections.

Common Pitfalls in Schematic Interpretation

1. Color code shifts: Early production runs used solid-colored wires (e.g., purple for alternator exciter), while later batches added a stripe (purple/black) for the same function. Verify against the date code stamped on the harness cover.
2. A/C vs. non-A/C variants: Compressor clutch relays differ; the former includes a time-delay module absent in base models. Mistaking these can lead to incorrect voltage readings at the compressor plug.
3. Tachometer wiring: Models with the 273 V8 use a dedicated pickup wire at the distributor, whereas the Slant-6 employs a resistor network tied to the ignition coil. Reversing these connections risks damaging the tachometer circuit board.

If physical manuals are unavailable, the For Bodies Only Mopar forum hosts user-uploaded scans of dealer-install sheets that specify connector types (e.g., Molex 21-pin vs. AMP Junior Power Timer) for critical junctions like the dashboard harness. Always compare these with your car’s build sheet, which lists installed options and can be requested from government archives using the VIN.

Step-by-Step Wire Color Codes and Connector Identification

Begin with the instrument cluster. The *light green* wire supplies power to the fuel gauge, while the *orange* lead connects to the temperature sender. Verify these against the service manual’s pinout–any deviation signals corrosion or incorrect splicing. The *black/white stripe* grounds the gauges; test continuity with a multimeter before proceeding.

Locate the firewall bulkhead connector. The *yellow* wire feeds the headlamp switch, branching into *red* (high beam) and *dark blue* (low beam). Label each terminal with masking tape–factory harnesses often omit clear markings. For turn signals, trace the *light blue* (right) and *dark green* (left) wires from the flasher module to the steering column plug; intermittent operation typically stems from a faulty relay, not the wires themselves.

Examine the fuse block. The *pink* wire delivers constant 12V to the ignition coil, while the *brown* lead powers the heater blower. Use a test light to confirm voltage at both ends of these circuits–partial power indicates a blown fuse or corroded junction. The *dark brown* wire runs to the rear lights; check for voltage drops under load (expected: ≤0.5V). Replace any connectors showing green oxidation.

Inspect the alternator wiring last. The *white* wire carries voltage sensing, and the *red* lead connects to the battery positive. A missing diode trio in the alternator manifests as flickering dash lights–this requires replacing the voltage regulator, not rewiring. For accessory circuits, confirm the *violet* wire (radio) and *gray* wire (cigarette lighter) share the same 10A fuse; cross-test if one fails but the other works.

Troubleshooting Common Electrical Issues Using the Schematic

Start by isolating the circuit in question. Trace the color-coded lines from the fuse block to the component experiencing failure. The factory layout splits into primary and secondary circuits–identify which branch feeds the problematic system. For example, if the headlamps flicker, follow the yellow wire from the fuse (labeled “HEAD LAMPS”) through the dimmer switch and check for continuity at each connection point.

Use a multimeter to verify voltage drops across suspected corroded or loose terminals. Set the meter to DC 20V and probe both sides of a connector while the circuit is active. A reading above 0.5V indicates excessive resistance, often caused by oxidized contacts or frayed strands. Clean terminals with a wire brush and apply dielectric grease to prevent future oxidation.

Check ground integrity as a critical failure point. Many issues stem from poor chassis grounds, especially near the battery tray or engine block. Locate the black or black-striped wires terminating at the body or frame. Scratch the paint beneath the terminal ring to bare metal, secure the connection, and coat with corrosion inhibitor.

Symptom	Likely Circuit	Diagnostic Steps
Dash lights dim	Instrument voltage regulator	Test resistance across regulator terminals (should read ~3 ohms). Replace if out of spec.
Blower motor only works on high	Resistor block behind glovebox	Inspect resistor coils for burns. Verify continuity between connector pins.
No starter engagement	Solenoid activation circuit	Check voltage at starter relay during key turn (should show 12V). Bypass relay with jumper if needed.

Inspect wiring harness runs near heat sources or sharp edges. Exposed copper or melted insulation will short to adjacent wires. Use heat-shrink tubing to repair damaged sections, ensuring no bare strands remain. Secure harnesses away from exhaust manifolds with nylon zip ties.

Test relays for proper function. Remove the relay and connect a 12V power source to terminals 85 and 86. A click confirms coil operation; probe terminals 30 and 87 with a test light to verify contact closure. Replace silent or non-switching relays.

Evaluate the alternator output at the battery. With the engine running, measure voltage across the battery posts. Readings below 13.5V indicate a failing voltage regulator or bad diode trio. Check the field coil resistance (should be 2.5–5 ohms) before condemning the unit.

For intermittent failures, wiggle-test the harness while monitoring symptoms. Flex connectors at door jambs or under seats often break internally. A temporary connection loss during movement pinpoints the exact wire segment requiring repair or replacement.