Lincoln Electric SVM194-A service manual Theory of Operation

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E-10	THEORY OF OPERATION		E-10
When the idle switch is in the auto position, and		The current sensor PC board detects current flow
welding current is being drawn, the reed switch		in both the auxiliary and the weld circuits. When
CR2 is closed. This signals the idler PC board to		sufficient current is flowing in either of these cir-
deactivate the idle solenoid, allowing the governor		cuits, the lead connected to pin #31 is grounded,
to increase the engine speed to high RPM. When		signaling that high RPM is required.	When cur-
auxiliary power is being used, the current is		rent flow ceases, the lead connected to pin #31 is
passed through the toroidal current transformer.		disconnected from chassis ground, and the
This also signals the idler PC board to deactivate		engine idles down after the delay described
the idle solenoid.	When welding ceases or the	above.
auxiliary load is removed, a preset time delay of		The idle switch and the current sensing PC board
about 15 seconds begins. When this 15 second
delay has passed, the PC board activates the idle		are wired in parallel between chassis ground and
solenoid, as described above, and pulls the		the pin#31 circuit described above. When the idle
engine governor linkage to the low idle RPM posi-		switch is set to the high position, the contacts are
tion. If welding is resumed, or an auxiliary load is		closed and the ECU operates the engine continu-
applied during this delay, the engine RPM will		ously at high RPM. When the idle switch is in the
remain high.		Auto position, the contacts are open, and the cur-
When the idle switch is in the high position, the		rent sensor PC board controls whether the pin
		#31 circuit is grounded or open.
reed switch CR2 is bypassed, signaling the PC
board to leave the solenoid inactive

Classic® 300D Kubota (Codes: 11112, 11113, 11243, 11244, 11413, 11414, 11474, and 11475) The Kubota engine control unit (ECU) used in the Classic® 300D controls whether the engine oper- ates at high idle or low idle. Grounding pin #31 of the ECU signals that high RPM is required and the engine immediately accelerates to high idle RPM. Opening the circuit between pin #31and chassis ground will cause the engine RPM to drop to low idle speed, after a delay of about 15 sec- onds. If the chassis ground to pin #31 circuit re- closed during this delay, engine RPM will remain high.

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

CLASSIC® 300D & 300G