SERVICING
46
WARNING
Line Voltage now present.
2. Disconnect the 4-circuit harness connecting the control to the
electric heater kit.
3. Provide a thermostat demand for low stage auxiliary heat.
Measure the voltage between pins 1 and 3 at the onboard
electric heat connector. Voltage should measure 24VAC. Re-
place control if no voltage is present.
NOTE:
Allow for any built-in time delays before making voltage
measurements. Any electric heater faults that are present may
prevent the heater output from energizing. Verify that no heater
faults are present before making voltage measurements.
4. Provide a thermostat demand for high stage auxiliary heat
(W1 + W2). Measure the voltage between pins 1 and 3 at the
on-board electric heat connector. Measure the voltage be-
tween pins 2 and 3 at the on-board electric heat connector.
Voltage should measure 24VAC. Replace control if no voltage
is present.
Communications (Applies only to Systems with Compatible
ComfortNet
TM
Outdoor Unit and CTK0* Thermostat)
The integrated air handler control has some on-board tools that
may be used to troubleshoot the network. These tools are: red
communications LED, green receive (Rx) LED, and learn button.
These are described below
a. Red communications LED – Indicates the status of the network.
Refer to the Network Troubleshooting Chart for the LED status
and the corresponding potential problem.
b. Green receive LED – Indicates network traffic. Refer to the
Network Troubleshooting Chart for the LED status and the cor-
responding potential problem.
c. Learn button – Used to reset the network. Depress the button
for approximately 2 seconds to reset the network.
Voltages between the two data lines and between each data line
and common may be used to determine if the network is operat-
ing properly.
Do the following to measure the voltages on the communications
data lines.
WARNING
Disconnect ALL power before servicing.
1. With power on to the unit, measure voltage between terminal
"1" and terminal "C" on control board's thermostat connector.
Voltage should be as noted in the table below.
2. Measure voltage between terminals "2" and "C".
3. Measure voltage between terminals "1" and "2".
4. If voltages are different than stated in the table below, check
thermostat wiring for opens/shorts. Confirm that the BIAS
and TERM dipswitches are in the ON position.
5. The network troubleshooting chart on the next page provides
additional communications troubleshooting information.
Te rm ina ls
Nonim a l dc
Volta ge s
1 to C
> 2.5 Vdc
2 to C
< 2.5 Vdc
1 to 2
> 0.2 Vdc
S-50 CHECKING HEATER LIMIT CONTROL(S)
(OPTIONAL ELECTRIC HEATERS)
Each individual heater element is protected with an automatic
rest limit control connected in series with each element to prevent
overheating of components in case of low airflow. This limit con-
trol will open its circuit at approximately 150°F. to 160°F and
close at approximately 110°F.
WARNING
Disconnect ALL power before servicing.
1. Remove the wiring from the control terminals.
2. Using an ohmmeter test for continuity across the normally
closed contacts. No reading indicates the control is open -
replace if necessary. Make sure the limits are cool before
testing.
IF FOUND OPEN - REPLACE - DO NOT WIRE AROUND
.
S-52 CHECKING HEATER ELEMENTS
Optional electric heaters may be added, in the quantities shown
in the spec sheet for each model unit, to provide electric resis-
tance heating. Under no condition shall more heaters than the
quantity shown be installed.
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing. Multiple power sources
may be present. Failure to do so may
cause property damage, personal injury
or death.
1. Disassemble and remove the heating element(s).
2. Visually inspect the heater assembly for any breaks in the
wire or broken insulators.
3. Using an ohmmeter, test the element for continuity - no read-
ing indicates the element is open. Replace as necessary.
