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CBX40UHV
P48 5 Pin
P49 4 Pin
J48 Connector
installed on motor
P49 4 Pin
120v
0
230v
5
4
3
2
1
J48 Connector
24v Transformer
J49 Connector
P49 4 PIN
P48 5 PIN
Figure 16. Regal-Beloit — Troubleshooting
Indoor Blower Motor (B3) Control
Troubleshooting (Emerson)
NOTE: If the communication channel is disrupted (loss of
communication and and 24VAC) to the air handler control,
the motor will continue to operate at its current mode. This
means, if the motor is currently in idle, it will stay in idle
mode; if it is currently running, it will stay running at the
current operating point.
1. Disconnect three-wire harness from motor control
module.
A. If the plug terminals inside the module are
damaged.
B. If terminals are not damaged, proceed to next step.
2. Inspect the negative temperature coefficient (NTC)
thermistor (see figure 18) for any cracks or breakage.
A. If damaged, replace control.
B. If no damage is detected, proceed to next step.
3. Check the capacitors for any damage. Inspect for:
A. Bulging or swelling caps. If caps are bulging or
swollen, replace control.
B. If no damage is detected, proceed to next step.
4. Check resistance between each of the three pins on the
control module jack (see figure 18). Resistance
between any two terminals should be greater than 100
K ohms.
A. If resistance is less than 100 K ohms, replace
control.
B. If no damage is detected, proceed to next step.
NOTE — If your ohm meter is not an auto-ranging type,
please set it to the highest ohm scale (100 K ohms or
greater).
Scale
Measurement range in
words
ohms
2 M
two megohm-two million
ohms
0 - 2,000,000
200 K
two hundred kilo-ohm-two
hundred thousand ohms
0 - 200,000
20 K
twenty kilo-ohm-twenty
thousand ohms
0 - 20,000
2 K
two kilo-ohm two-thousand
ohms
0 - 2,000
200 two hundred ohms 0 - 200
Figure 17. Typical Digital Multimeter
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