Trane Voyager Commercial Installation & Operation Manual page 142

Diagnostics
Table 77. Troubleshooting (continued)
SYMPTOM
O. No Heat (TE's only) Electric
heat will not operate.
P. Evaporator coil freezes up
during low ambient operation.
Q. Economizer will not
operate.
R. Minimum position is at zero,
cannot be adjusted.
Economizer still modulates.
S. Economizer goes to
minimum position, and will not
modulate.
142
PROBABLE CAUSE
1. Heater contactor(s) have
failed.
2. Heater element temperature
limit(s) is open.
3. Wiring or terminal failure.
4. Heater Element(s) has failed.
5. RTRM is defective.
1. System low on refrigerant
charge.
2. System low on air flow.
3. Outdoor Air Sensor (OAS) has
Failed.
4. FrostatTM has Failed
1. Economizer connector not
plugged into unit wiring harness.
2. Economizer Actuator (ECA)
has failed.
3. Wiring or terminal failure.
4. ECA is defective.
1. Remote Minimum position
potentiometer has failed.
2. Minimum position
potentiometer has failed.
1. OAS has failed.
2. MAS has failed.
RECOMMENDED ACTION
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. 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. Check for wiring, or terminal failure in control and
power ircuit. Repair or replace if necessary.
4. Check element and circuit integrity. Repair or
replace as necessary. Replace open elements.
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.
1. Leak check, repair, evacuate, and recharge system
as necessary.
2. Check return air for obstruction or dirty filters.
Check fan wheels, motors, and belts.
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. Check Frostat Switch
1. Check connector, and connect if necessary.
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. Check wiring and terminals. Repair or replace if
necessary.
4. Perform the ECA Test Procedures discussed
previously.
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. Rotate the onboard minimum position
potentiometer knob. If ECA does not drive to different
minimum position, replace ECA.
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. 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.
RT-SVX34C-EN