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Situation
Cause/Solution
(Test in order indicated)
When the 691 System is activated,
the brakes will not lock-up and the
power unit does not run.
1. No electric power.
Check the battery, fuse, and wiring connections.
2. High Pressure Switch is inoperative.
Activate the 691 System. If "PS1 (lock)" LED is on, unplug pressure switch 1.
If pump runs, replace pressure switch 1 (high pressure switch) or check for a
short to ground in the wiring.
3. The Power Unit or Control Module is inoperative.
Activate the 691 System. If "Motor Up" LED is on, check for 12 VDC at the
power unit connector. Unplug the power unit and attach a voltmeter (+ to
blue, - to green) to the connector leading to the control module. If 12 VDC is
present, replace the power unit. If 12 VDC is not present, replace the control
module.
4. The Control Module is not receiving an input signal.
Activate the 691 System. Check "+ Ext" and "- Ext" LED's. If neither are on,
check that a ground signal is present at the gray lead in the main wiring har-
ness, or the green lead from the user interface; or that a positive signal is
present on the brown wire in the main wiring harness. If not, determine the
reason and correct.
When the 691 System is activated,
the brakes will not lock-up and the
power unit continues to run.
1. The fluid level in the reservoir is low.
Deactivate the 691 System. Verify that the power unit is mounted level.
Remove the reservoir breather/filler plug and fill the reservoir with proper fluid
to within 1/4" of top. Reinstall breather/filler plug.
2. Hydraulic leak in either the 691 System or service brake system.
Inspect all tubing and connections for leaks and tighten or replace as
necessary.
3. The actuator is not functioning properly.
Activate the 691 System. Check the vehicle master cylinder reservoir for
excessive fluid level. This condition indicates that the seals in the actuator
are allowing 691 System fluid to leak into the vehicle service brake system.
Refer to TABLE 1 (pages 19 & 20) for the proper actuator repair kit. Replace
the seals in the actuator. NOTE: The vehicle brake system may need to
be flushed and refilled.
4. The power unit is not properly building pressure.
Replace the power unit. (no test to troubleshoot this condition).
The 691 System will activate and
lock-up the brakes but the power
unit keeps running.
1. High pressure switch is inoperative.
Active the 691 System . If "PS2" LED is off, replace pressure switch 1
(high pressure switch).
The power unit does not operate to
release the brakes when the 691
System is deactivated.
1. No electric power.
Check the battery, fuse, and wiring connections.
2. Low pressure switch is inoperative.
Deactivate the 691 system. If "PS2" LED is off, replace pressure switch 2
(low pressure switch).
3. The power unit or control module is inoperative.
Deactivate the 691 System. If the "Motor Down" LED is on, check for
12 VDC at power unit connector. Unplug power unit and attach a voltmeter
(- to blue, + to green) to the connector leading to control module. If 12 VDC is
present, replace the power unit. If 12 VDC is not present, replace control
module.
The brakes release but the 691
Power Unit does not stop run-
ning.
1. Low pressure switch is inoperative.
Deactivate the 691 System. If the "PS2" LED is on, replace pressure switch 2
(low pressure switch).
2. The control module is inoperative.
Deactivate the 691 System. If "Motor Down" LED is off, replace the control
module.