Loader Bobcat 773. Manual - part 111

ACTUATOR VOLTAGE TEST

Procedure

With Test Harness;

The test harness (MEL1554) and a digital multimeter are
necessary to complete the following procedure.

Disconnect the actuator wire connector (Item 1) [A] for
the tilt or (Item 2) [A] for the lift circuit from the controls
harness.

NOTE: Each actuator has to be checked separately.

Install the test harness (Item 1) [B].

Turn the key to the ON position with engine OFF.

With a digital multimeter, take a voltage reading at the four
prong terminal connector (Item 2) [B].

The sensor supply voltage between terminal 1 (ground)
and terminal 3 [C] should be 4.3

0.1 volts

(5.0

0.1 volts

Hall–Effect).

The signal voltage reading between terminal 1 (ground)
and terminal 2 [C] should be from 1.55 to 1.85 volts (1.80
to 2.15 volts*).

NOTE: Terminal 4 [C] is an open terminal not used at

this time.

Without Test Harness;

A digital multimeter is necessary to complete this test.

The wiring harness connectors must remain connected to
complete this test.

If the test harness (MEL1554) is not available the sensor
supply voltage test 4.3

0.1

volts ( 5.0

0.1

volts*) can

be taken between terminal 1 and terminal 3 on the tilt
control harness (Item 1) [D] and the lift control harness
(Item 2) [D].

The signal voltage reading 1.55 to 1.85 volts (1.80 to 2.15
volts*) can be taken between terminal 1 and terminal 2 on
the tilt control harness (Item 1) [D] and the lift control
harness (Item 2) [D].

Wire Code For Tilt Control Harness: (Item 1) [D]

Terminal 1

Light Blue/Yellow

. . . .

Terminal 2

LIght Blue/White

. . . .

Terminal 3

Light Blue

. . . .

Terminal 4

Open

. . . .

Terminal 5

Pink/White

. . . .

Terminal 6

Light Blue/Red

. . . .

Terminal 7

Black

. . . .

Terminal 8

Pink/Yellow

. . . .

Wire Code For Lift Control Harness: (Item 2) [A]

Terminal 1

Light Green/Yellow

. . . .

Terminal 2

Light Green/White

. . . .

Terminal 3

Light Green

. . . .

Terminal 4

Open

. . . .

Terminal 5

Brown/White

. . . .

Terminal 6

Light Green/Orange

. . . .

Terminal 7

Black

. . . .

Terminal 8

Brown/Yellow

. . . .

* Hall–Effect (Identified by yellow push button float
switch on left–hand handle.

N–17781

P–13754

N–17781

–10–8–

Service Manual

773 BICS Loader

Revised June 01

N–17782

ACTUATOR VOLTAGE TEST (Cont’d)

Procedure (Cont’d)

Diagnosis Results For Tilt Actuator (top) Sensor Supply Voltage Test;

If the sensor supply voltage is 4.3

0.1 volts (5.0

0.1 volts Hall–Effect), continue on and check the signal voltage.

If the sensor supply voltage is less than 4.3

0.1

volts (5.0

0.1 volts*) or 0 volts, check the PWM fuse, check for shorts

or opens in the wiring harness. If there are no apparent shorts or opens change the AHC/PWM controller. (See Page

10–13.)

If the sensor supply voltage is more than 4.3

0.1

volts (5.0

0.1 volts*) check for a short of the power wires in the wiring

harness. If there are no apparent shorts change the AHC/PWM controller. (See Page 10–15.)

Diagnosis Results For Tilt Actuator Signal Voltage Test;

If the signal voltage is in the range of 1.55 to 1.85 volts (1.80

2.15 volts*), the system is functioning properly. The nominal

voltage reading is 1.72 volts (2.0 volts*).

If the signal voltage is not in the range of 1.55 to 1.85 volts (1.80

2.15 volts*) check the hydraulic control valve spools

for a centering problem or replace the actuators. (See Page 10–29.)

Handle Out (Toward Side Screen):

1. Stop engine. Raise operator cab.

2. Connect the remote start switch (MEL1429A) to the loader.

3. Turn key to ON position with engine OFF to get a code indication from the indicator lights on the left control handle.

4. Check the sensor supply voltage. (See Page 10–8.)

5. Check the system to make sure it is functional, with no blinking indicator lights.

6. Move right AHC handle toward the side screen to full stroke. Hold in position and and take a voltage reading.

The voltage reading must be 0.13 volts (0.15 volts*) or greater.
If the voltage reading is less than 0.13 volts (0.15 volts*, replace the actuator. (See Page 10–29.)
While holding the handle toward the side screen turn the key to OFF position and wait five seconds..

7. Continue to hold the handle toward the side screen and turn the key to the ON position. Take a voltage reading.

(You will have a one blink alarm on the right indicator light.)
The voltage reading should be between 1.55 to 1.85 volts (1.80 to 2.15 volts*).
If the voltage is above 1.85 volts (2.15 volts*), repeat steps 5 thru 7, if the voltage is still above 1.85 volts (2.15
volts*) change the actuator.
If the voltage is below 1.55 volts (1.80 volts*) complete the following tests: (See Step 11 Below; Tests a & b.)

Handle In (Toward Center Of Cab):

8. Turn the key to OFF position and wait five seconds, then turn key to ON position. Check the system to make sure

it is functional, with no blinking indicator lights.

9. Move right AHC handle toward the center of the cab to full stroke. Hold in position and take a voltage reading.

The voltage reading must be 3.2 volts (3.72 volts *) or less.
If the voltage reading is more than 3.2 volts (3.72 volts *), check for shorts in the electrical connections, or replace
the actuator. (See Page 10–29.)

10. While the handle is held toward the center of the cab, turn the key to OFF position and wait five seconds.

11. Continue to hold the handle toward the center of the cab and turn the key to the ON position. Take a voltage reading.

(You will have a one blink alarm on the right indicator light.)
The voltage reading should be between 1.55 to 1.85 volts (1.80 to 2.15 volts*).
If the voltage is below 1.55 volts (1.80 volts*), repeat steps 8 thru 11 if the voltage is still below 1.55 volts (1.80
volts*) change the actuator.
If the voltage is above 1.85 volts (2.15 volts*) complete the following tests:

a. Remove the pin from the actuator to the control spool. Watch the spool, if the spool continues to move toward
neutral after the pin is removed, replace the actuator. Also check the mounting hardware on the actuators and
control valve for wear and correct torque.

b. If the spool does not move, check the control valve for a sticky spool or sticky centering mechanism. Also check
the mounting hardware on the actuators and control valve for wear and correct torque.

* Hall–Effect (Identified by yellow push button float switch on left–hand handle.

–10–9–

Service Manual

773 BICS Loader

Revised Nov. 01

ACTUATOR VOLTAGE TEST (Cont’d)

Procedure (Cont’d)

Diagnosis Results For Lift Actuator (bottom) Sensor Supply Voltage Test;

If the sensor supply voltage is 4.3

0.1

volts (5.0

0.1 volts Hall–Effect), continue on and check the signal voltage.

If the sensor supply voltage is less than 4.3

0.1

volts (5.0

0.1 volts*) or 0 volts, check the PWM fuse, check for shorts

or opens in the wiring harness. If there are no apparent shorts or opens change the AHC/PWM controller. (See Page

10–13.)

If the sensor supply voltage is more than 4.3

0.1

volts (5.0

0.1 volts*) check for a short of the power wires in the wiring

harness. If there are no apparent shorts change the AHC/PWM controller. (See Page 10–15.)

Diagnosis Results For Lift Actuator Signal Voltage Test;

If the signal voltage is in the range of 1.55 to 1.85 volts (1.80 to 2.15 volts*), the system is functioning properly. The nominal

voltage reading is 1.72 volts (2.0 volts*).

If the signal voltage is not in the range of 1.55 to 1.85 volts (1.80 to 2.15 volts*) check the hydraulic control valve spools

for a centering problem or replace the actuators. (See Page 10–29.)

Handle Out (Toward Side Screen):

1. Stop engine. Raise operator cab.

2. Connect the remote start switch (MEL1429A) to the loader.

3. Turn key to ON position with engine OFF to get a code indication from the indicator lights on the left control handle.

(See Page 10–6.)

4. Check the sensor supply voltage. (See Page 10–8.)

5. Check the system to make sure it is functional, with no blinking indicator lights.

6. Move left AHC handle toward the side screen to full stroke. Hold in position and take a voltage reading.

The voltage reading must be 0.13 volts (0.15 volts*) or greater.
If the voltage reading is less than 0.13 volts (0.15 volts*), replace the actuator. (See Page 10–29.)

7. While holding the handle toward the side screen turn the key to OFF position.

8. Wait five seconds, then put the handle to the float position. Turn the key to ON position and take a voltage reading.

(You will have a one blink alarm on the left indicator light.)
The voltage reading should be between 1.55 to 1.85 volts (1.80 to 2.15 volts*).
If the voltage is above 1.85 volts (2.15 volts*), repeat steps 5 thru 8, if still above 1.85 volts (2.15 volts*), change
the actuator.
If the voltage is below 1.55 volts (1.80 volts*) complete the following tests: (See Step 12 Below; Tests a & b.)

Handle In (Toward Center Of Cab):

9. Turn the key to OFF position and wait five seconds, then turn key to ON position. Check the system to make sure

it is functional, with no blinking indicator lights.

10. Move left AHC handle toward the center of the cab to full stroke, in float position. Take a voltage reading.

The voltage reading must be 4.17 volts (3.72 volts*) or less.
If the voltage reading is more than 4.17 volts (3.72 volts*), check for shorts in the electrical connections, or replace
the actuator. (See Page 10–29.)

11. While the handle is in float position, turn the key to OFF position. Wait for five seconds.

12. Continue to keep the handle in the float position. Turn the key to ON position. Take a voltage reading.

(You will have a one blink alarm on the left indicator light.)
The voltage reading should be between 1.55 to 1.85 volts (1.80 to 2.15 volts*).
If the voltage is below 1.55 volts (1.80 volts*), repeat steps 9 thru 12, if the voltage is still below 1.55 volts (1.80
volts*) change the actuator.
If the voltage is above 1.85 volts (2.15 volts*) complete the following tests:

* Hall–Effect (Identified by yellow push button float switch on left–hand handle.

–10–10–

Service Manual

773 BICS Loader

Revised Nov. 01

HANDLE CONTROL UNIT TEST

Procedure

Right Handle Test With Test Harness;

Raise the operator cab. (See Page 1–1.)

Connect the remote start switch. (See Page 1–1.)

The test harness (MEL1555) and a digital multimeter are

necessary to complete the following procedure.

Disconnect the handle control harness (Item 1) [A].

Install the test harness (Item 1) [B].

Move handle to the neutral position.

Turn the key to the ON position with the engine OFF.

With a digital multimeter take a voltage reading at the four

prong terminal connector (Item 2) [B].

The sensor supply voltage between ground, terminal 1
and terminal 3 [C] should be 4.3

0.1

volts (5.0

0.1

volts Hall–Effect).

The signal voltage reading between the ground, terminal
1 and terminal 2 [C] should be 1.7 to 2.1 volts (1.97

2.44

volts*).

NOTE: Terminal 4 [C] is an open terminal not used at

this time.

Right Handle Test Without Test Harness;

A digital multimeter is necessary to complete this test.

For the switch handle harness connector color code. (See

Page 10–24.)

The test must be run at the eight pin switch handle

connector (Item 1) [A]. The wiring harness connectors

must remain connected to complete this test.

Check the sensor supply voltage (4.3

0.1

volts) (5.0

0.1

volts*) between terminal G (Pink/Black) and terminal

F (Pink/Red).

Check the signal voltage between terminal G (Pink/Black)

and terminal H (Pink/Green). The voltage should be

between 1.7 to 2.1 volts (1.97 to 2.44 volts*).

Diagnosis Results for both Tests;

If the sensor supply voltage is 4.3

0.1

volts (5.0

0.1

volts*), continue on and check the signal voltage.

If the sensor supply voltage is less than 4.3

0.1

volts

(5.0

0.1

volts*) or 0 volts, check the PWM fuse, check

for shorts or opens in the wiring harness. If there are no

apparent shorts or opens change the AHC/PWM

controller. (See Page 10–15.)

If the sensor supply voltage is more than 4.3

0.1

volts

(5.0

0.1

volts*) check for a short to a power wire in the

wiring harness. If there are no apparent shorts, change

the AHC/PWM controller. (See Page 10–15.)

If the signal voltage is in the range of 1.7 to 2.1 volts (1.97

to 2.44 volts*) the system is functioning properly. The

nominal voltage reading is 1.89 volts (2.2 volts*). If the

signal voltage is not in the range of 1.7 to 2.1 volts (1.97

to 2.44 volts*) change the handle controller.

* Hall–Effect (Identified by yellow push button float
switch on left–hand handle.

N–17536

P–13754

–10–11–

Service Manual

773 BICS Loader

Revised Nov. 01

P–17780

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