Description

Solar 170-III Workshop Manual – The OEM File You Need for the EPOS System

If you’re digging into a Solar 170-III excavator and the EPOS-III system goes dark on you – no display, no auto-idle, weird power modes – you don’t have time to chase generic wiring sketches. That CPU-driven control system processes sensor data, adjusts pump output, and can lock you out of diagnostics if you miss a step. The factory Workshop Manual for the Solar 170-III is 35 pages of exactly what the dealer techs use. No third-party rewrite. No guessing on proportional reducing valve signals.

EPOS-III System: Why This Manual Is Critical

The EPOS system on the Solar 170-III manages hydraulic power output through RPM sensing and hydraulic cross-sensing. When you’re trying to diagnose a “fail-safe” mode or a self-diagnostic fault code, the manual walks you through the CPU, display, and sensor circuit. Page 1 starts with the electrical system general description – the same page that explains how the controller adjusts pump input power from 68% to 100% depending on load. If you skip the OEM wiring diagram and use an aftermarket guess, you risk shorting the proportional reducing valve circuit. Don’t do that.

35 Pages of Factory Electrical Diagnostics

At 35 pages, this workshop manual isn’t a tome. It’s targeted. Covers the electrical control box, throttle controller, control motor for the fuel injection pump, and the two rotary dials for arm/boom speed vs. swing priority. You also get the override logic for the auto-idle function – that four-second neutral timer that shuts the engine down to low idle. Need the exact resistance values for the sensor inputs? It’s in the manual. No guessing.

Does This Manual Cover Hydraulic and Engine Tuning?

Yes – but from the electrical control perspective. The EPOS-III system ties engine RPM to pump load. The manual explains how the work mode options (digging, loading, leveling, lifting) and power mode settings (68%, 85%, 100% engine power) are selected and how the controller changes signal current to the proportional reducing valve. If you’re rebuilding the hydraulic pump or replacing a sensor, you need the factory voltage and pressure references. The manual gives you those specs without filler.

Source Authenticity: OEM vs Aftermarket Wiring Diagrams

I’ve seen aftermarket “service manuals” for the Solar 170-III that list the EPOS controller pins wrong. They swap the arm dump and boom up signal lines. That mistake sends you chasing a ghost when the combined operation dial doesn’t work. The OEM workshop manual on this site is a direct scan of the document Solar 280LC-III 1998 Parts Catalog – OEM Factory Specs uses the same electrical legend format. If you need the control valve exploded view for the 170-III’s pump system, the Solar 280 1998 Parts Catalog – OEM Factory Control Valve Exploded View gives you the cross-reference. The Solar 470Lc-V Parts Catalog – OEM Factory Specs for Excavator is also from the same factory source. No reprints. No copy.

Get the Right Torque Data for Solar 170-III

The manual includes the torque specs for the pump mounting bolts, swing motor fasteners, and track drive components. I’ve seen DIYers snap bolts on the final drive because they used a generic torque chart. The Solar factory values are specific to the 170-III. The manual also covers the overheat protection circuit – when coolant temp exceeds 225°F (107°C), the controller drops engine speed and pump load. If you’re installing a new radiator or sensor, those torque values and wire routing matter. The Manual Transmission section from the factory archive follows the same format, and if you need the general transmission theory, the Manual Transmission reference from Wikipedia is a good background read. But for the 170-III, stick to the OEM book.

Frequently Asked Questions

Does the Solar 170-III Workshop Manual include wiring diagrams?

Yes. The manual starts with the electrical system general description and covers the full EPOS-III wiring for sensors, CPU, display, proportional reducing valve, and throttle controller. Wire colors and connector pinouts are factory-original.

Can this manual help diagnose the auto-idle function?

Yes – it explains the four-second timer logic, the throttle controller signal, and the fail-safe default mode. If the engine won’t drop to low idle, you can trace the circuit.

What is the page count?

35 pages.

Is this a reprint or a scan of the original factory document?

It’s a direct scan of the OEM workshop manual. No third-party editing. No added fluff. The EPOS-III system description on page 1 matches the original Solar documentation exactly. I trust it because I’ve used it to fix a 170-III that had a stuck proportional reducing valve. The voltage readings were spot-on.

If you’re working on a Solar 170-III and you need the factory procedure for the EPOS system, electrical diagnostics, or hydraulic control setup, don’t waste hours with guesswork. Access the Factory Manual and get the OEM data on your bench.