Electrical Maintenance
65
Zone 2 Evaporator Will Not Terminate
Defrost
If the defrost termination switch does not
terminate Defrost less than 45 minutes after
Defrost was initiated, the TG-V Controller should
terminate Defrost.
The Multi-Temp TG-V Controller will record
alarm code 47 if the R11 circuit stays grounded
and the defrost termination on time limit is
unsuccessful.
Zone 2 Evaporator Sticks In Defrost
Indefinitely
If the unit remains stuck in Defrost indefinitely,
check the Zone 2 defrost relays, the R11 circuit
and the TG-V Controller.
NOTE: If the Multi-Temp TG-V Controller has
recorded Alarm Code 47, check the R11 circuit
for a ground first.
1. Check the Zone 2 defrost relays:
If the unit remains on Defrost indefinitely,
remove the jumper from between the R8N and
R8NN terminals on the relay board. The Zone
2 defrost relays should open (de-energize)
immediately. If the relays open (de-energizes),
move to step 2. If a relay fails to open, replace
the relay.
2. Disconnect the cab box harness and check the
R11 circuit:
If the defrost relays opened (de-energized)
when the jumper was removed, disconnect the
cab box harness from the back of the TG-V
Controller and check the R11 circuit for
continuity to CH (ground). If the R11 circuit is
grounded, repair it. If not, move to step 3.
3. Check the TG-V Controller:
The integral defrost timer in the TG-V
Controller should terminate the Defrost cycle
after 45 minutes regardless of the evaporator
temperature or amount of frost or ice on the
evaporator coil. If not, test the TG-V
Controller. See “Field Test Procedure for
Multi-Temperature In-Cab TG-V Controllers”
on page 72.
Zone 2 Evaporator Continuously Fails to
Terminate Defrost In Less than 45 Minutes
If the unit continually fails to complete the
Defrost cycle in less than 45 minutes, and cycles
between Cool and Defrost, check the evaporator
coil temperature, RHGS, CIS, PV, RTPS, RTPC,
refrigerant charge, Zone 2 fan relay, defrost
termination switch and the R12 wire.
1. Check the evaporator temperature:
Make sure the evaporator temperature is
actually above 52 F (11 C) if the unit will not
terminate Defrost. Use a test thermometer to
check the temperature.
If the evaporator temperature does not rise
enough to bring the out of Defrost, the CIS,
RHGS, PV, RTPS, or the RTPC may be faulty,
or the unit may be low on refrigerant.
If the Zone 2 fan relay fails to open and/or the
Zone 2 evaporator fans continue to run, the
evaporator temperature may not rise enough to
terminate Defrost. To test the Zone 2
evaporator fans, start the condensing unit and
run the Zone 2 evaporator in Defrost. The
Zone 2 evaporator fans should not be running.
If the fans are running, remove the Zone 2 fan
relay, the fans should stop running. If the fans
stop running, the relay is defective. If the fans
do not stop, there is a short in the RFM circuit.
2. Check the operation of the defrost termination
switch.
If the unit will not come out of Defrost,
disconnect the R12 wire from the defrost
termination switch. If the unit shifts back to
Cool, the defrost termination switch is not
opening and should be replaced. If the unit
remains in Defrost, move to step 3.
3. Check the R12 circuit for a ground:
If the unit remains in Defrost, use an
ohmmeter to check the R12 circuit for a
ground. If the R12 circuit is grounded, find the
grounded portion and repair it.
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