Description

Bomag BC 670 1996 Electrical Schematic – Factory OEM Wiring Diagram

If you’re chasing a short in a Bomag BC 670 1996 Electrical Schematic and the harness looks like it’s been chewed by a badger, you already know the price of guessing. One wire pinched against the frame, one relay swapped with the wrong amp rating, and you’re looking at a fried control module or a fire. This is the factory drawing set – 35 pages of the actual circuit diagrams Bomag’s engineers used when they built the machine. Not a redrawn, translated, or condensed version. The real thing.

35 Pages of OEM Wiring – What’s Inside

This manual breaks the electrical system into ten functional groups. The table of contents lists them exactly as they appear on the schematic sheets: Funktion, Versorgung, Starten, Überwachung, Warnanlage, Kabine, Heizung, Belüftung, Schaltschutzeinrichtung, and Kontrollmodul. Each group has its own sheet number and drawing number. For example, the supply section is sheet 990 101 55, and the starting unit is sheet 990 101 56. You get the full circuit diagram, not just a simplified block diagram. The legend tells you thick lines are standard wiring, thin lines are printed-circuit-board connections. That distinction saved me half an hour on a previous Bomag job – the PCB traces were intermittent, and I’d have wasted time chasing harness wires.

Supply and Starting Unit – Where the Power Flow Begins

Versorgung (Supply) covers the voltage transformer (24V to 12V for the cab accessories), generator, sockets, and battery. Page 2 shows the 24V/12V split, the generator output, and the battery connections. Starten (Starting) on page 3 includes the ignition switch, main fuse, starter motor, 12V relay, ether starting solenoid valve, engine shut-down circuit, timer, reset, and fuel cut-off switch. If your BC 670 cranks but won’t fire, trace the ether solenoid circuit – there’s a relay K2.3 that controls it, and the schematic gives you the exact pin numbers on the connector. You’ll need a multimeter with a diode test function and a set of terminal picks to back-probe the connector without damaging the pins.

Monitoring Unit – Why Sensor Diagnostics Are Critical

Überwachung is the monitoring section – 20 sub-circuits covering every sensor and switch on the machine: RPM meters, hydraulic oil pressure, engine oil pressure, coolant temperature, hydraulic oil temperature, fuel level, pressure switches, travel lever position, lubrication system proximity switches, coolant fan, brake release, central lubrication, air cleaner restriction, and two contamination sensors. Each sensor is drawn with its supply voltage and ground path. If you’re seeing a false warning light, you can isolate the sensor circuit without tearing the harness apart. Use a breakout lead to measure voltage drop across the sensor while the engine runs. The schematic shows the differential pressure switch for the air filter – a common failure point that triggers a false “restricted air” warning. Don’t throw a new filter at it until you’ve tested the switch per the diagram.

Does This Manual Cover the Cab and Heating Circuits?

Yes. Kabine (cab), Heizung (heating unit), and Belüftung (air conditioning) are included on sheets 990 101 57 and 990 101 42. The cab section has the wiper, lights, and horn circuits. The heating unit shows the blower motor and thermostat wiring. Air conditioning includes the compressor clutch relay and pressure switches. These are often overlooked until the operator complains about no heat or a dead A/C. Having the factory drawing means you can check the fuse and relay locations without guessing which aftermarket color code they used.

Source Authenticity – Factory vs. Aftermarket Schematics

I’ve seen aftermarket schematic books that list generic connector pinouts – they’re close but not exact. Bomag changed wire colors between 1995 and 1997, and the aftermarket guys miss those updates. This is the OEM print from Bomag GmbH, Boppard, drawn in September 1996. The drawing numbers match the ones stamped on the machine’s electrical panels. Trusting a third-party diagram when you’re dealing with a 24V system that can arc-weld a screwdriver is asking for trouble. Automotive Industry Overview covers the stakes, but you already know – one wrong connection and the repair bill doubles. This is the same document the dealer’s service tech would call up on his laptop.

Get the Right Tools Before You Start Probing

Before you open this schematic, put a fused jumper wire, a digital multimeter rated for CAT III 600V, and a set of wire piercing probes in your box. The wiring uses a mix of 1.5mm² and 2.5mm² conductors – don’t use a test light on the CAN bus lines, you’ll pop the transceiver. The manual doesn’t list torque specs because it’s an electrical schematic, but the Bomag BC 670 RB Training Manual – Factory Specs & Repair Docs”>Bomag BC 670 RB Training Manual – Factory Specs & Repair Docs covers those. For a deeper look at other Bomag models, check the Bomag BW 24 R 2001 Training Manual – Factory Specs & Repair”>Bomag BW 24 R 2001 Training Manual – Factory Specs & Repair. If you’re working on smaller equipment, the Mag International T-MAG XC Mini Truck Owner’s Manual”>Mag International T-MAG XC Mini Truck Owner’s Manual might be useful, but this Bomag schematic is the only one you need for the BC 670 electrical system.

FAQ

Does this manual include torque specs?

No. This is an electrical schematic, not a service manual.

Can I use this to trace a no-start condition?

Yes, the starting unit section (sheet 990 101 56) shows the ignition switch, main fuse, starter relay, and ether start solenoid. You’ll need a multimeter and the wiring color codes from the diagram. Follow the power path from the battery through the main fuse (F4.6) to the ignition switch (M01), then to the starter relay (K2.3). The schematic labels every connector pin – X2.7, X4.4, X5.7 – so you can meter each junction without guessing. If the starter doesn’t crank, check that the 12V relay is getting ground from the engine ECU. The diagram includes the engine shut-down circuit that can interrupt the start signal if the timer or reset module is faulty. I’ve seen a bad timer keep the fuel cut-off solenoid closed; the schematic shows how to bypass it temporarily for testing.

If you’re tired of flipping through blurry photocopies and guessing which wire goes where, this is the document that pays for itself on the first job. Stop risking melted harnesses and fried modules. Access the Factory Manual and get the real Bomag BC 670 Electrical Schematic – the same one the factory techs use.