Nortek YDHA - 7.3 Troubleshooting the Heat Section; 7.3.1 General Troubleshooting - Electric Heat Section

Form O-Y, PN 273647R5, Page 46
PROBLEM PROBABLE CAUSE REMEDY
Unit does
not operate
1. No power to unit 1. Turn on power; check supply fuses or main circuit breaker.
2. Blown fuses 2. Check and replace if necessary.
3. Defective or incorrect wiring. 3. Check wiring and connections. Refer to wiring diagram provided with
unit.
4. Defective or burned out control
transformer
4. Check secondary voltage with voltmeter. Replace if necessary.
Fan
operates
but element
does not
heat
1. Dirty lters 1. Check lters and clean or replace if necessary.
2. Defective air proving switch 2. Check and replace if necessary.
3. Blown element fuses 3. Check and replace element fuses if necessary.
Insufcient
heat
1. Burned out element 1. Turn off power and check element resistance with ohmmeter. Replace
if open.
2. Blown fuses 2. Check and replace if necessary.
3. Cycling on limit control 3.
a) Check air throughput (temperature rise).
b) Check motor rpm against nameplate rating. Replace motor if speed is
too slow.
c) Defective limit control. Check wiring and connections. Check continuity
through control and replace if necessary.
4. Defective or incorrect wiring. 4. Check wiring and connections. Refer to wiring diagram provided with
unit.
7.3 Troubleshooting the Heat Section
7.3.1 General Troubleshooting - Electric Heat Section (Option E__)
LED State
Indicates Additional Information
Color CODE
All Solid Digital compressor
controller failure
The installed digital compressor controller can be tested
to verify that it is working properly. In each test, 24VAC
must be supplied to 24VAC and 24COM. For output
test, 24-250VAC must be supplied to L1 and L2.
Input Tests - 1) Thermistor Input - Disconnect thermistor
(T1 & T2); LED should display Code 6.; and 2) Demand
Input - Disconnect unit controller (C1 & C2); LED
should display Code 5 unless a previous alert code was
present.
Output Tests - 1) Contactor Output - while the controller
is powered off (no supply voltage to 24VAC and
24COM), disconnect signal wire from C1 & C2; add
jumper wires from P3 to C2 and from P1 to C1; re-apply
power to 24VAC and 24COM. If functioning normally,
same voltage should be read across M1 and M2 as
across L1 and L2, unless an LED ALERT code is
present.; and 2) Unloader Output - while controller is
modulating the unloader solenoid (whenever the yellow
LED is lit), voltage across U1 and U2 should be the
same as L1 and L2.
All Flashing 24VAC Supply too low for
operation
7.0 Troubleshooting (cont'd)
7.2 Troubleshooting Compressor Digital Controller (cont'd)