Carrier 38mvc018 3 Service Manual

							21
REFRIGERANT LINES
General refrigerant linesizing:
1. The 38MVC/MVQ units are shipped with a full charge of
R410A refrigerant. All charges, line sizing, and capacities
are based on runs of 25 ft (7.6 m). For runs over 25 ft (7.6
m), consult long--line section on this page for proper charge
adjustments.
2. Minimum refrigerant line length between the indoor and
outdoor units is 10 ft. (3 m).
3. Refrigerant lines should not be buried in the ground. If it is
necessary to bury the lines, not more than 36--in (914 mm)
should be buried. Provide a minimum 6--in (152 mm)
vertical rise to the service valves to prevent refrigerant
migration.
4. Both lines must be insulated. Use a minimum of 1/2-- in.
(12.7 mm) thick insulation. Closed--cell insulation is
recommended in all long--line applications.
5. Special consideration should be given to isolating
interconnecting tubing from the building structure. Isolate
the tubing so that vibration or noise is not transmitted into
the structure.
SThe following maximum lengths are allowed:
REFRIGERANT LINE LENGTHS ft. (m)
Unit SizeMax Line
LengthMax Elevation
(ID over OD)Max Elevation
(OD over ID)
9K65 (20)35 (11)35 (11)12K65 (20)35 (11)35 (11)18K100 (30)50 (15)50 (15)24K100 (30)60 (18)60 (18)
SThe following are the piping sizes.
PIPE SIZESUnit SizeMix PhaseVapor9K1/4”3/8”12K1/4”1/2”18K1/4”1/2”24K3/8”5/8”
RefrigerantCharge
REFRIGERANT CHARGE lb. (kg)Unit SizeAir ConditionerHeat Pump
9K2.3 (1.0)2.4 (1.1)12K2.9 (1.3)3.0 (1.4)18K4.4 (2.0)TBD24KTBDTBD
SAbove charge is for piping runs up to 25 ft. (7.6 m).
SFor piping runs greater than 25 ft. (7.6 m), add 0.1 oz. of
refrigerant per foot of extra piping up to the allowable
length.Long Line Applications, 38MVC
Units:
1. A crankcase heater should be added for line lengths longer
than 25 ft (7.62 m) to prevent the migration of refrigerant to
the compressor during the “OFF” cycle.
2. A field fabricated wind baffle is recommended.
3. No change in line sizing is required.
4. Add refrigerant per table below.
ADDITIONAL CHARGE TABLE
Unit
Size
To t a l
Line Length,
ftAdditional Charge, oz.
Min.Max.10 --- 25 ft
(3.05 --- 7.62m)> 2 5 --- 6 5 f t
(7.62 --- 19.81m)> 6 5 --- 1 0 0 f t
(19.81 --- 30.48m)
9K
cool
only
10
65
none0.1 oz per
foot
9K
hp
12K
cool
only
12K
hp
18K
cool
only1000.1 oz. per
foot
5. Reduction in capacity due to long lines can be calculated
from the chart below.
CAPACITY LOSS
Capacity,%Loss
Line Length, ft
Cooling:254565100
9&12KBTU/Hmodels0%2%5%
18 & 24 KBTU/H models0%2%4%7%
Heating:
9&12KBTU/Hmodels0%7%11%
18 & 24 KBTU/H models0%7%11%15%
38/40MVC, MVQ 
						

							22
SYSTEM EVACUATION AND
CHARGING
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment
damage or improper operation.
Never use the system compressor as a vacuum pump.
CAUTION!
Refrigerant tubes and indoor coil should be evacuated using the
recommended deep vacuum method of 500 microns. The alternate
triple evacuation method may be used if the procedure outlined
below is followed. Always break a vacuum with dry nitrogen.
SYSTEM VACUUM AND CHARGE
Using VacuumPump
1. Completely tighten flare nuts A, B, C, D, connect manifold
gage charge hose to a charge port of the low side service
valve. (See Fig. 18.)
2. Connect charge hose to vacuum pump.
3. Fully open the low side of manifold gage. (See Fig. 19)
4. Start vacuum pump
5. Evacuate using either deep vacuum or triple evacuation
method.
6. After evacuation is complete, fully close the low side of
manifold gage and stop operation of vacuum pump.
7. The factory charge contained in the outdoor unit is good for
up to 25 ft. (8 m) of line length. For refrigerant lines longer
than 25 ft (8 m), add 0.1 oz. per foot of extra piping up to
the maximum allowable length.
8. Disconnect charge hose from charge connection of the low
side service valve.
9. Fully open service valves B and A.
10. Securely tighten caps of service valves.
Outdoor UnitIndoor UnitRefrigerant
Service Valve
Low Side
High Side A
BC
D
A07360
Fig. 18 – Service Valve
Manifold Gage
500 microns
Low side valveHigh side valve
Charge hoseCharge hose
Vacuum pump
Low side valve
A07361
Fig. 19 – ManifoldDeep Vacuum
Method
The deep vacuum method requires a vacuum pump capable of
pulling a vacuum of 500 microns and a vacuum gage capable of
accurately measuring this vacuum depth. The deep vacuum method
is the most positive way of assuring a system is free of air and
liquid water. (See Fig. 20)
500
MINUTES 01234567 1000 1500LEAK IN
SYSTEM
VACUUM TIGHT
TOO WET
TIGHT
DRY SYSTEM 2000
MICRONS
2500 3000 3500 4000
4500
5000
A95424
Fig. 20 – Deep Vacuum Graph
Triple Evacuation
Method
The triple evacuation method should only be used when vacuum
pump is only capable of pumping down to 28 in. of mercury
vacuum and system does not contain any liquid water.
Refer to Fig. 21 and proceed as follows:
1. Pump system down to 28 in. of mercury and allow pump to
continue operating for an additional 15 minutes.
2. Close service valves and shut off vacuum pump.
3. Connect a nitrogen cylinder and regulator to system and
open until system pressure is 2 psig.
4. Close service valve and allow system to stand for 1 hr. Dur-
ing this time, dry nitrogen will be able to diffuse throughout
the system absorbing moisture.
5. Repeat this procedure as indicated in Fig. 21. System will
then be free of any contaminants and water vapor.
CHECK FOR TIGHT, DRY SYSTEM
(IF IT HOLDS DEEP VACUUM)EVACUATE
BREAK VACUUM WITH DRY NITROGEN
WAIT
EVACUATE
RELEASE CHARGE INTO SYSTEM
BREAK VACUUM WITH DRY NITROGEN
EVACUATE
WAIT
A95425
Fig. 21 – Triple Evacuation Method
Final Tubing
Check
IMPORTANT: Check to be certain factory tubing on both
indoor and outdoor unit has not shifted during shipment.
Ensure tubes are not rubbing against each other or any sheet
metal. Pay close attention to feeder tubes, making sure wire ties
on feeder tubes are secure and tight.
38/40MVC, MVQ 
						

							23
CONTROL SYSTEM
The 40MVC/MVQ unit is equipped with a microprocessor control to perform two functions:
1. Provide safety for the system
2. Control the system and provide optimum levels of comfort and efficiency
The main microprocessor is located on the control board of the fan coil unit (outdoor units have a microprocessor too) with thermistors
located in the fan coil air inlet and on the indoor coil. Heat pump units have a thermistor on the outdoor coil. These thermistors monitor the
system operation to maintain the unit within acceptable parameters and control the operating mode.
SYSTEM SAFETIES
SafetyCooling OnlyHeat Pump9K012K018K024K09K012K018K024K3MinTimeDelayXXXXXXXXOver Current Protection On CompressorXXXXXXXXIndoor Coil Freeze ProtectionXXXXXXXXCondenser High Temperature ProtectionXXXXIndoor Evaporator High TemperatureXXXX
3MINUTETIMEDELAY
In order to protect the compressor, there is a 3 minute delay on break even if the control is calling for heating or cooling.
COMPRESSOR OVERCURRENT PROTECTION
Overcurrent protection can result due to any of the following:
SThe ambient temperature is to high
SLocked rotor on the compressor
SBlockage in refrigeration circuit (cap tubes, for example)
SOutdoor air is blocked or restricted
The compressor current is monitored continuously and protection is provided as shown below:
 3 sec
 5 min
1 sec
Normal
Indoor fan: On
compressor: On
outdoor fan: OnOutdoor fan 
off (heating)
Indoor fan low
speed (cooling)Compressor off
(after 5 minutes)Compressor off
(after 3 seconds)Current down
Current up
A08117
Fig. 22 – Compressor Overcurrent Protection
If the compressor is stopped 4 times at the 5 minute limit or 1 time at the 3 second limit, the system will be locked off and the main power will
have to be reset before the system can be restarted.
Time LimitCompressor Current
38MVC(Q)009 --- 138MVC(Q)012 --- 138MVC(Q)012 --- 338MVC(Q)018 --- 338MVC(Q)024 --- 3
3SEC14 A18 A11 A14 A23 A
5MIN12 A16A9A12 A21 A
ISEC10.5 A14 A7A11 A18 A
NORMAL9A12.5 A6A10 A16 A
38/40MVC, MVQ 
						

							24 Indoor Coil Freeze
Protection
The indoor coil can freeze due to any of the following:
SLow system charge
SReduced indoor airflow
SRestricted refrigerant flow
SLow ambient temperature (outdoor)
SLow load (indoor)
In cooling mode, the thermistor located on a return bend of the
indoor coil monitors the coil temperature continuously. Any time
the coil temperature drops below the TE5 limit for five consecutive
minutes, the compressor and outdoor fan will be switched off until
the coil temperature rises above the TE6 as shown below:
Compressor and outdoor
fan off (after 5 mins)Compressor and
outdorr fan on
EVAP temp. downEVAP temp. up
TE5 TE6T 
(Evap Temp.)
A08118
Fig. 23 – Indoor Coil Freeze Protection
Parame te rCoil Temperature ° F (° C)40MVC(Q)
009 --- 140MVC(Q)
012 --- 140MVC(Q)
018 --- 340MVC(Q)
024 --- 3
TE539 (4)41 (5)36 (2)36 (2)TE650 (10)54 (12)54 (12)54 (12)
Condenser High TemperatureProtection
Condenser high temperature can occur due to any of the following
conditions:
SHigh outdoor ambient
SOutdoor fan blocked
SOutdoor coil blocked
The outdoor coil thermistor on a heat pump unit continuously
monitors the temperature of the outdoor coil. Anytime the coil
temperature exceeds the TE10 limit, the compressor is switched off
and the outdoor fan continues running to reduce the coil
temperature. When the coil temperature drops below the TE11
limit, the compressor is switched back on as shown below:
Compressor on 
Outdoor fan on
COND temp. down
TE11 TE10 TCOND temp. up
Compressor off
Outdoor fan on
A08119
Fig. 24 – Condenser High Temp Protection
Parame te rCondenser Temp.
°F (°C)
38MVQ018 --- 338MVQ024 --- 3TE10149 (63)158 (70)TE11131 (55)149 (65)
Indoor High TemperatureProtection
High indoor coil temperature (in heating mode) can occur due to
any of the following:
SHigh outdoor ambient temperature
SIndoor fan blocked
SIndoor coil blocked (including dirty filters)
The indoor coil thermistor on a heat pump unit continuously
monitors the temperature of the indoor coil during heating
operation. Anytime the coil temperate exceeds the TE8 limit, the
outdoor fan is switched off. If the coil temperature continues to
climb and exceeds the TE7 limit, the compressor is switched off.
When the coil temperature drops below the TE9 limit, the
compressor and outdoor fan are switched back on as shown
below:
TE9 TE8 TE7 T
T temp. up
Compressor on 
Fan on
T temp. down
Compressor off 
Fan off
Compressor on
Fan off
A08120
Fig. 25 – Indoor High Temperature Protection
Parame te r
Condenser Coil Temp.
°F (°C)
40MVQ
009 --- 140MVQ
012 --- 140MVQ
018 --- 340MVQ
024 --- 3
TE7140 (60)140 (60)145 (63)145 (63)TE8129 (54)129 (54)129 (54)129 (54)TE9118 (48)118 (48)122 (50)122 (50)
SEQUENCE OF OPERATION
Interface
A wireless remote control, supplied with the unit, is the interface
between the fan coil and the user. The wireless remote control has
the following characteristics:
SCapable of displaying_Cand_F with_C being the default
setting. To change the default setting, refer to the Owner’s
Manual or push the recessed F/C button once using a paper
clip or similar object*.
SThe remote control setpoint range is from 62_F(17_C) to
88_F(30_C) in increments of 2_F(1_C).
SThere is a dedicated cooling only and heat pump remote
control.
SThe wireless remote control has an operating range of 25 ft.
(7.62 m).
SThe same remote control can be used to control more than one
unit.
SIf the remote control is lost, damaged, or the batteries are
exhausted, the system can be operated by using the manual
button (forced Auto) located under the front panel.
Manual button
A07364
Fig. 26 – Manual Button Location on Unit
* On units produced during week 12 (2008) and later. Units
produced before week 12 have dedicated_Cor_F controls.
38/40MVC, MVQ 
						

							25
MODES OF OPERATION
The units have 5 main operating modes:
1. Fan Only
2. Cooling
3. Heating (heat pumps only)
4. Auto
5. Dehumidification (Dry)
The units have 2 other modes (manual operation) that are operated
in unique situations:
1. Auto Forced Mode (Emergency)
2. Test Mode
Fan Mode
Only
In this mode, the system circulates the room air without changing
the room air temperature.
Cooling
Mode
In this mode, the system cools and dries the room air with the fan
running continuously, either at a selected fan speed or Auto fan
speed. The fan runs even when the compressor cycles off. This
feature enhances room comfort and efficiency of the system.
When the unit is operating in cooling, two sub modes can also be
selected:
1. Sleep Mode is an energy saving feature that changes the set
point automatically.
2. Turbo Mode is a comfort feature on the 9k and 12k units
where the set point is reached quickly by having the fan run
on high speed regardless of the speed that has been selected.
Compressor and Outdoor Fan
Operation
The compressor and outdoor fan motor cycle on and off based on
the conditions of the set point and the room temperature as shown
below. There is no minimum run time.
T  = Room Temperature 
Ts = Set Point TemperatureCompressor off
fan off Compressor and
outdoor fan on
 Room temp. down
0 1.8°FT-Ts
 Room temp. up
A08106
Fig. 27 – Compressor and Outdoor Fan -- Cooling Mode
Indoor Fan
Operation
When in cooling mode, the fan runs continuously either at the
chosen set speed , or in Auto mode, where the speed is determined
by the microprocessor based on the difference between the room
temperature and the temperature set point as shown below:
Room temp. upRoom temp. down
T= Room Temperature
Ts = Set Point Temperature
9.0 °F 7.2 °F 1.8 °F T-Ts
Low fanHigh fan
Med fan
A08107
Fig. 28 – Auto Fan -- Cooling ModeSleep
Mode
When in cooling mode, additional energy savings can be realized
by selecting the Sleep setting. When the Sleep setting is selected,
the temperature set point is adjusted automatically as shown below:
Set point
Time (hour) 121.8
°F
1.8
°F
A08108
Fig. 29 – Sleep Mode
The unit will shut off 7 hours after the Sleep Mode is selected.
Turbo
Mode
When in cooling mode, selecting Turbo will allow the indoor unit
to satisfy the temperature set point as quickly as possible. In Turbo
Mode, the indoor fan will shift to high speed and either run
continuously for 20 minutes or until the user pushes the Turbo
button again, at which point the fan speed will return to the original
setting.
Heating
Mode
In this mode, the system heats the room air with the indoor fan
running at either the selected speed or on Auto. As in the cooling
mode, the indoor fan will run continuously unless interrupted by
the cold blow algorithm. This algorithm will not allow the fan to
run if the indoor coil temperature drops below a preset value.
The sleep function can be selected while the unit is running in the
Heating Mode. Defrost is controlled by the on--board
microprocessor.
Compressor and Fan
Operation
The compressor and outdoor fan cycle on and off based on the
actual room temperature versus the set point as shown below.
When the compressor starts, it will run continuously for 7 minutes
even if the set point condition is satisfied.
The 4 -- way value is energized in heating and will stay energized for
2 minutes after the mode is changed into a non--heating mode.
Compressor on 
outdoor fan off
Room temp. upRoom temp. downCompressor off 
outdoor fan on 
Ts+5.4* Ts+3.6* Ts TT    = Room Temperature 
TS = Set Point Temperature 
* For 9k & 12k Units Only.  For 18k and 24k units, numbers will be 5.4 and 7.2 respectively.
A08109
Fig. 30 – Compressor and Outdoor Fan -- Heating Mode
38/40MVC, MVQ 
						

							26 Auto
Fan
When the fan speed is set to Auto, the fan will run at either the
medium or low speed based on the difference between the room
temperature and the set point temperature as shown below:
Room temp. upRoom temp. down
T- Ts0 Med. SpeedLow. Speed
3.6°FT   = Room Temperature 
Ts = Set Point Temperature
A08112
Fig. 31 – Auto Fan -- Heating Mode
Manual Indoor
Fan
The indoor fan will run continuously in heating at the set fan speed
(even if the compressor cycles off) unless the indoor coil
temperature begins to drop. When the coil temperature drops to
the TE3 limit, the 18k and 24k unit indoor fan switches to low
speed. On the 9k and 12k unit the indoor fan switches to ultra low
speed. When the coil temperature drops to the TE4 limit, the
indoor fan on all systems shuts off to prevent cold blow as shown
below. The cold blow algorithm also applies to the auto fan
setting.
T temp. upT temp. down
Fan o ff
Low Speed /  
Ultra Low SpeedSet fan speed
TE4 TE1 TE3 TE2 T
(Coil temp.)
A08111
Fig. 32 – Manual Indoor Fan -- Heating Mode
Parame te rIndoor Coil Temperature ° F (° C)40MVQ
009 --- 140MVQ
012 --- 140MVQ
018 --- 340MVQ
024 --- 3
TE188 (31)88 (31)77 (25)82 (28)TE293 (34)91 (33)90 (32)93 (34)TE386 (30)81 (27)86 (30)90 (32)TE472 (22)68 (20)68 (20)75 (24)
SleepMode
When in heating mode additional energy savings can be realized
by selecting the Sleep setting. When the Sleep setting is selected,
the temperature set point is adjusted automatically as shown below:
Set Point
Time (hour) 121.8ºF 1.8ºF
A08110
Fig. 33 – Sleep Mode -- Heating
The unit will shut off 7 hours after the Sleep mode is selected.
Defrost
Defrost on heat pump units is controlled by the microprocessor and
is initiated if either of the following conditions occur:
1. The outdoor coil temperature is lower than 32_F(0_C) for
more than 40 minutes and during that period, the coil
temperature is continuously lower than 26.6_F(--3_C) for 3
minutes.
2. If the first condition does not occur within 90 minutes of
termination of the last defrost cycle.
The defrost cycle will terminate 10 minutes after initiation or when
the coil temperature reaches 68_F(20_C). At the end of the
Defrost cycle the timer resets automatically.
The cycles of defrost algorithm are shown below:
Compressor
4-way valve
Outdoor fan
Indoor fanDefrost 10 or 6 minutes
On
Off
5s
10s25s
2s
A08114
Fig. 34 – Defrost Cycle
Auto
Mode
When the Auto setting is selected, the microprocessor looks at the
difference between the room temperature (T) and the set point
(TS). The algorithm determines which mode the unit will run in as
shown below:
Heating (fan only in cooling) Fan only         Cooling
-1.8
°F              3.6°F
T-T S
A08115
Fig.35–AutoMode
When the unit shifts modes, it will remain in that mode for at least
15 minutes while the algorithm ignores the difference between T
and TS. This ensures that the unit cannot change modes too
frequently.
38/40MVC, MVQ 
						

							27 Dry (Dehumidification)
Mode
When more humidity control is desired, the Dry setting can be
selected. Lower humidity is achieved when the microprocessor
adjusts the indoor fan speed and compressor cycling by comparing
the room temperature (T) and the set point temperature (TS).
There are two different control algorithms:
Size 9k and 12 k
units:
T = TS + 3.6 -- the compressor will run for 6 minutes and the
indoor fan will run at low speed. The compressor will be off for 4
minutes and the indoor fan will run in ultra low speed.
TS = T < TS + 3.6 -- The compressor will run for 5 minutes and the
indoor fan will run at low speed. The compressor will be off for 5
minutes and the indoor fan will run in ultra low speed.
T < TS -- The compressor will run for 4 minutes and the indoor
fan will run at low speed. The compressor will be off for 6 minutes
and the indoor fan will run in ultra low speed.
Size 18k and 24k
units:
These units do not have ultra low speed. When set for
dehumidification, the indoor fan runs at low speed and the
compressor cycles based on the difference between T and TS.
Manual
Operation
The unit can be set for Forced Auto or Forced Cooling manually
by pushing the Manual button once or twice as shown below:
Remote
modeForced
autoForced
cooling
Push 3 TimesPush Once Push Twice
A08116
Fig. 36 – Manual OperationForced Auto (Emergency
Operation)
Forced Auto option allows operation of the unit if the remote
control is lost or the batteries have expired. When the system is in
Forced Auto, it will run with a default set point of 75.2_F. While
in Forced Auto, the system will respond to signals from the remote
control.
Forced Cooling
Operation
This option is used for diagnostic purposes. The system is forced
to run in cooling for 30 minutes.
After 30 minutes, the 9k and 12k systems will switch to Dry mode
with a default set point of 75.2_F. The 18k and 24k systems will
switch to Forced Auto mode. When the system is in Forced
Cooling mode, it will not respond to signals from the remote
control. The only way to exit the Forced Cooling mode is to push
the manual button once to switch the system to remote control
mode.
38/40MVC, MVQ 
						

							28
TROUBLESHOOTING
This section provides the required flow charts to troubleshoot problems that may arise.
NOTE:Information required in the diagnoses can be found either on the wiring diagrams or in the appendix.
Required
Tools:
The following tools are needed when diagnosing the units:
SDigital multimeter
SScrew drivers (Phillips and straight head)
SNeedle-- nose pliers
Recommended
Steps
1. Refer to the diagnostic hierarchy chart below and determine the problem at hand.
2. Go to the chart listed in the diagnostic hierarchy and follow the steps in the chart for the selected problem.
DIAGNOSTIC HIERARCHY
Unit has a problem
Unit displays a 
diagnostic codeUnit not running and
no diagnostic codeUnit running but not 
optimally
Refer to page ---
appropriate diagnostic chart  Go to chart # 7Go to chart # 8 & 9
* For EEROM error, replace the indoor microprocessor board
Unit has a problem
Unit displays a 
diagnostic codeUnit not running and
no diagnostic codeUnit running but not 
optimally
Refer to page A8 & A9
identify error code*and use Go to chart Go to chart #
* For EEROM error, replace the indoor microprocessor board
A08165
For the ease of service, the systems are equipped with diagnostic
code display LED’s on both the indoor and outdoor units. The
outdoor diagnostic display is an LED on the outdoor unit board
and is limited to very few errors. However, it is useful in
identifying special error codes like a failure of the outdoor coil
sensor on heat pumps. The indoor diagnostic display is a
combination of flashing LED’s on the display panel on the front of
the unit. If possible always check the diagnostic codes displayed on
the indoor unit first.
The diagnostic codes for the indoor and outdoor units are listed in
appendix A8 and A9.
Problems may occur that are not covered by a diagnostic code, but
are covered by the diagnostic flow charts starting with the
diagnostic hierarchy. These problems will be typical air
conditioning mechanical or electrical issues that can be corrected
using standard air conditioning repair techniques.For problems requiring measurements at the control boards please
note the following:
1. Always disconnect the main power.
2. When possible check the outdoor board first.
3. Start by removing the outdoor unit top cover.
4. Reconnect the main power
5. Probe the outdoor board inputs and outputs with a digital
multi-- meter referring to the wiring diagrams and
input/output charts found in the appendix.
6. Connect the red probe to hot signal and the black probe to
the ground or negative.
7. Note that some of the DC voltage signals are pulse will give
continuously variable readings.
8. If it is necessary to check the indoor unit board you must
start by disconnecting the main power.
9. Next remove the front cover of the unit and then control
box cover.
10. Carefully remove the indoor board from the control box,
place it face up on a plastic surface (not metal).
11. Reconnect the main power and repeat steps 5,6, and 7.
12. Disconnect main power before reinstalling board to avoid
shock hazard and board damage.
38/40MVC, MVQ 
						

							29
CHART 1 -- INDOOR FAN SPEED OUT OF CONTROL
Reset main power and 
restart system using remote.
Problem persists?
Replace indoor fan motor
No further action is 
requiredNo
Yes
Check IFM output and input
on indoor board.
Values good?
Yes
Check motor connection.
Connection good?  No
Fix connection
Yes
No
Replace indoor board
Reset main power and 
restart system using remote.
Problem persists?
Replace indoor fan motor
No further action is 
requiredNo
Yes Yes
Check motor connection.
Connection good?  No
Fix connection
Yes
No
Replace indoor board
A08166
38/40MVC, MVQ 
						

							30
CHART 2 -- TEMPERATURE SENSOR
Reset main power and 
restart system using remote.
Problem persists?
Appendix 6
No further action is 
requiredNo
Yes
Check input and output 
on indoor or outdoor board.
Yes
Check sensor connector
at ID or OD board 
Connection good?  No
Fix connection
Yes
No
Replace board
Check sensor resistance.
No
Yes Yes
No
Yes
No
No
Replace sensor
No
Double check connection, 
for corrosion or high 
resistance.
YesYes
A08167
38/40MVC, MVQ