142 RT-SVX34C-EN
Diagnostics
O. No Heat (TE's only) Electric
heat will not operate.
1. Heater contactor(s) have
failed.
1. Check for 24 VAC at AH, BH,CH, and DH contactor
coils. If 24 VAC is present on a call for heat, and the
contacts do not close, the contactor has failed.
2. Heater element temperature
limit(s) is open.
2. Check line voltage between the element
temperature limit terminals located in heat section. If
line voltage is present, the limit is open. Repair
heating unit, or replace limit(s) as needed.
3. Wiring or terminal failure.
3. Check for wiring, or terminal failure in control and
power ircuit. Repair or replace if necessary.
4. Heater Element(s) has failed.
4. Check element and circuit integrity. Repair or
replace as necessary. Replace open elements.
5. RTRM is defective.
5. Check RTRM heat outputs. "First stage", locate P2
connector, connected to J2 on the RTRM. Locate wire
65E at terminal P2-9, measure between 65E and
ground. If 24 VAC is present, repeat #3 above. If 24
VAC is not present, the RTRM has failed. "Second
stage", Locate 67B wire at terminal P2-8, measure
between 67B and ground. 24 VAC should be present.
If 24 VAC is not present, the RTRM has failed.
P. Evaporator coil freezes up
during low ambient operation.
1. System low on refrigerant
charge.
1. Leak check, repair, evacuate, and recharge system
as necessary.
2. System low on air flow.
2. Check return air for obstruction or dirty filters.
Check fan wheels, motors, and belts.
3. Outdoor Air Sensor (OAS) has
Failed.
3. Check OAS at connector P8 by disconnecting P8
from J8 on the RTRM. Check resistance between P8-
1 and P8-2, refer to the Resistance versus
Temperature chart. Replace sensor if necessary.
4. FrostatTM has Failed 4. Check Frostat Switch
Q. Economizer will not
operate.
1. Economizer connector not
plugged into unit wiring harness.
1. Check connector, and connect if necessary.
2. Economizer Actuator (ECA)
has failed.
2. Verify that 24 VAC is present between ECA
terminals 24 VAC and Common. Place the unit in econ
test mode, economizer actuator should drive open. In
any other unit test mode, economizer actuator should
drive to minimum position. If ECA does not drive as
specified, replace ECA.
3. Wiring or terminal failure.
3. Check wiring and terminals. Repair or replace if
necessary.
4. ECA is defective.
4. Perform the ECA Test Procedures discussed
previously.
R. Minimum position is at zero,
cannot be adjusted.
Economizer still modulates.
1. Remote Minimum position
potentiometer has failed.
1. With the main power off, check the resistance
between terminals P and P1 at the ECA by rotating the
remote minimum position potentiometer knob.
Resistance should be 50 to 200 Ohms.
2. Minimum position
potentiometer has failed.
2. Rotate the onboard minimum position
potentiometer knob. If ECA does not drive to different
minimum position, replace ECA.
S. Economizer goes to
minimum position, and will not
modulate.
1. OAS has failed.
1. Check the OAS at connector P8 by disconnecting P8
from J8 on the RTRM. Check resistance between P8-
1 and P8-2, refer to the Resistance versus
Temperature Chart. Replace sensor if necessary.
2. MAS has failed.
2. Check the MAS at connector P23 by disconnecting
P23 from MAT on the ECA. "MAT" is marked on the
actuator. Check for resistance between P23-1 and
P23-2, refer to the Resistance versus Temperature
Chart. Replace sensor if necessary.
Table 77. Troubleshooting (continued)
SYMPTOM PROBABLE CAUSE RECOMMENDED ACTION
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