Carrier 69NT40-541-500 Operation And Service Manual page 131

a. Obtain a grounding wrist strap (Carrier Transicold P/N 07-00304-00) and a static dissipation mat (Carrier
Transicold P/N 07-00304-00). The wrist strap, when properly grounded, will dissipate any potential electro-
static buildup on the body. The dissipation mat will provide a static-free work surface on which to place and/
or service the controller.
b. Disconnect and secure power to the unit.
c. Place strap on wrist and attach the ground end to any exposed unpainted metal area on the refrigeration
unit frame (bolts, screws, etc.).
d. Carefully remove the controller, refer to
possible. Place the module on the static mat.
e. The strap should be worn during any service work on the controller, even when it is placed on the mat.
7.20.2 Controller Troubleshooting
A group of test points (TP) (see
(see schematic diagram,
Use a digital voltmeter to measure AC voltage between TPs and ground (TP9), except for TP8.
TP 1 - NA
TP 2 - This test point enables the user to check if the internal protector for the compressor motor (IP-CP) or high
pressure switch is open.
TP 3 - This test point enables the user to check if the water pressure switch (WP) contact is open or closed.
TP 4 - This test point enables the user to check if the internal protector for the condenser fan motor (IP-CM) is open
or closed.
TP 5 - This test point enables the user to check if the internal protectors for the evaporator fan motors (IP-EM1 or
IP-EM2) are open or closed.
TP 6 - This test point enables the user to check if the controller water tank heater relay (TQ) is open or closed.
TP 7 - This test point is not used in this application.
TP 8 - This test point is not applicable to the units covered herein.
TP 9 - This test point is the chassis (unit frame) ground connection.
TP 10 - This test point enables the user to check if the heat termination thermostat (HTT) contact is open or closed.
Section
Figure 7.24) are provided on the controller for troubleshooting electrical circuits
Section 8). A description of the test points follows:
7.20.4. Do not touch any of the electrical connections if
NOTE
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