Lincoln Electric SVM175-A Engine Idle System Idle Switch Operation:, Idle Solenoid Operation:

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Engine Idle SystemIdle Switch Operation:

When the engine is started it operates at high RPM. If

the idle switch is in the high position the automat-

ic idle system is inactive and the engine will continue to

operate at high RPM.

If the engine is started with the idle switch in the auto

position, or if the idle switch is moved to the

auto position while the engine is running, a 12 second

on the control PC board is started. If there is no signif-

icant current flow detected from the weld or auxiliary

outputs during that 12 second time, the idle solenoid

will be activated, dropping the engine RPM to preset

low idle speed. If a load is applied during the 12 sec-

ond delay,the engine speed will remain high.

While operating at low RPM; if the idle switch is moved

to high, or there is a load detected from either the weld

of auxiliary outputs, the idle solenoid will be deactivat-

ed, allowing the engine governor to increase the RPM

to high speed.

When the idle switch is in the “auto” position and the

machine is under load and running at high RPM. If the

load is removed, the machine will continue to run at

high RPM for 12 seconds, then drop to low RPM,

unless a load is re-applied during that 12 second delay

Idle Solenoid Operation:

The engine speed is controlled by a two stage solenoid

connected to the engine speed control lever. When the

solenoid is inactive, the engine operates at high RPM,

and is controlled by the governor. When the solenoid

is activated, the speed control lever is pulled to a pre-

set low RPM setting.

The solenoid is powered by battery voltage directly

from the run/stop switch. The control PC board and

pull coil PC board activate the pull and hold coils by

providing a path to ground.

When the machine goes to low idle speed, the control

PC board grounds the hold coil of the idle solenoid and

at the same time it sends a signal of about +14VDC to

the pull coil PC board. This DC signal remains at

+14VDC for the entire time that the hold coil is active.

Whenthe signal is applied to the Pull coil PC board, the

board will energize the pull coil of the idle solenoid for

a brief moment, normally less than one second. This

momentary activation of the pull coil supplies the need-

edpower to reliably move the speed control lever to the

low idle position.

THEORY OF OPERATION

E-3 E-3

RANGER 305D

NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.

ROTOR

ENGINE

PROTECTION

CIRCUIT

ENGINE

PROTECTION

LIGHT

RUN

STOP

SWITCH

GLOW

PLUG

BUTTON

12V.

BATTERY

STARTER

ENGINE

SENSORS GLOW

PLUGS ENGINE

ALTERNATOR

START

BUTTON IDLE

SOLENOID

PULL

COIL HOLD

COIL

FUEL

PUMP

FUEL

SOLENIOD

PULLCOIL

PCBOARD

CHARGING

SYSTEMLIGHT

(CODE10926ONLY)

WELD

WINDING

STATOR

EXCITER

WINDING

120/240 VAC

AUX.WINDING

42VAC

WINDING

240

VAC

CURRENT

SENSOR 14

120

vac

FLASHING RECEPTACLES

HOLDCOIL

AMPHENALS

OUTPUT

CONTROL

ARC

CONTROL

MODE

SWITCH

WELDING

TERMINAL

SWITCH

IDLE

SWITCH

AMP

DISPLAY

VOLT

DISPLAY

WELDCONTROL

P.C. BOARD

POWER

MODULE

IGBTs

SHUNT

CHOKE -

FIGURE E.3 –ENGINE IDLE SYSTEM, IDLE SWITCH & IDLE SOLENOID