GILLIG LOW FLOOR, Руководство по обслуживанию

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Heating & Air Conditioning
435
Troubleshooting
NO WATER FLOW OR NO HEAT CONDITION
If you have a “no heat” condition and believe that the pump is not operating properly, follow these steps
to determine if the pump has failed or if some other part of the system is causing the no heat condition.
1. Hook up a clamp-on style DC ammeter with a range of 500 mA to 10 amps DC.
2. Move any loom covering on the leads of the pump if so equipped so you can access the red (+)
and black (–) leads.
3. Attach the ammeter clamp over the positive (+) red lead.
4. Energize the power to the pump. Check to verify that the proper voltage is being applied to the
pump motor using a voltmeter. The proper voltage in a 24 VDC system is approximately 27.5
VDC.
5. Check the ammeter reading. The following readings indicate various conditions:
a. 2.5 amps to 5.5 amps for a 24 VDC system: This is the normal current range. The pump is
functioning properly.
b. .5 amps to 1.0 amps: Either the pump has decoupled from the motor due to an obstruction
in the pump, or the pump has locked up due to being run dry. This reading indicates that the
motor is operating properly. The pump portion will need to be repaired or replaced depending
on the extent of the damage.
c. 7.0 amps or higher for a 24 VDC system: The pump is being obstructed, but not to the point
of complete failure, or the pump has been run dry and is in the process of failing. This in-
creased current may also be the beginning of motor bearing failure. Check to verify that the
motor runs properly without the pump attached. If the motor still exhibits high current, then
the bearings should be replaced.
d. 100 mA or less: Check the supply voltage to verify that the proper voltage is being applied to
the pump motor. Also check the polarity to insure that it is correct, (+) red, (–) black (nega -
tive). If the polarity is reversed, the motor will not operate. Hook up the leads correctly and
the motor will operate properly. This is a safety feature. The motor will not be damaged by
hooking up the polarity reversed. If the polarity is correct and the ammeter still reads 100 mA
or less, then the motor is not operating. The motor can be removed from the pump without
draining the system. See Figure 10- 3. Remove the four cap screws on the interface piece. The
pump will remain in the system.
Different bus systems will operate at different set points. The amp
reading for properly operating pumps should remain fairly consistent
throughout the same bus model and year.