DOMETIC Display QHT Marine TW & DX Gray

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  • Display QHT Marine DX & TW Gray P/N 722200200

Dometic SMXQht Keypad/Display for DX & TW

Basic Operation & Programmer’s Pocket Guide:


Factory Memory Reset
To restore all programming functions to the Factory Setting, first switch to Off Mode and then
simultaneously press and hold the POWER and MODE keys. Hold keys for three seconds
while “00” flashes in the display. Successful memory reset is indicated by a “1” flashing back
and forth across the display; release keys. System returns to the Off Mode.
NOTE: Performing a Factory Memory Reset will not change the value of Function Numbers 21
& 22. Also note that Function Number 2, which displays Fahrenheit or Celsius, reverts back
to °F each time.

Fault Code Displays

If an operational failure occurs, such as low voltage or high/low pressure, a flashing fault code
message will be displayed. Fault code displays are canceled by pressing the POWER key.

Fault Code Indication Result
LO / AC Operating voltage remained below acceptable
limit for three minutes or more (100V for a 115V
system or 200V for a 230V systems).
HI / PS* Head pressure above 425 PSI. Shutdow
LO / PS** Head pressure below 30 PSI. Shutdown
PE Software program error. Shutdown

Basic Operation

Turning the System On:
Press the POWER or MODE keys to turn the system on. In three seconds, the system will
start operating in whatever mode it was running prior to the last shut down. Press the MODE
key prior to three seconds (while the display is flashing) to change mode before system
starts, or any time to change the mode while the system is on. The modes available are: Cool,
Heat, Auto Switchover (automatically switches from Cool to Heat Mode), or Dehumidification
Mode. A solid dot will light up next to the words COOL or HEAT when the compressor is on
and running in that mode.

Selecting the Setpoint:
Press the Up or Down Arrow keys to adjust the setpoint (press and hold keys to scroll); wait
three seconds after powering up system. The word SET will appear in the display while
setpoint is being adjusted. The setpoint range is 55-99°F (10-40°C). Inside cabin temperature
is continuously displayed.

Adjusting the Fan Speed:
The FAN key is used to adjust the fan speed while in Manual Fan Speed Mode and to switch
from Manual to Automatic Fan Speed Modes. The fan may be run manually whether the
system is on or off. The word MANUAL appears in the display while in that mode. Automatic
Fan Speed Mode may be operated only when the system is on. Fan behavior also depends
on how the Fan Mode function is programmed - “C” for continuous or “I” for intermittent
running with the compressor (see Programming below).

Dimming the Display:
Press the MODE and Up Arrow keys simultaneously and repeatedly to select the display
brightness setting.

Backlight Mode:
While in the Sleep Mode (backlight is off) press any button to light the display, and then
operate as usual.

Important Memory Function:
After changing modes, programming settings, setpoint, etc., wait at least 30 seconds before
turning off main power supply in order for new settings to be maintained in memory.

SMXht keypad/display must be in the Off Mode prior to entering Programming Mode; pressing
the POWER key turns the display off or on. Once in the Off Mode, then:

  1. Simultaneously press and hold the MODE and Down Arrow keys for three seconds.
    Successful entry into the Programming Mode is indicated by the word “PROG” and a
    flashing “1” in the display.
  2.  Use the Up or Down Arrow keys to scroll until the desired program Function Number is
  3.  Press the MODE key to enter the desired function. The current value and the word
    “PROG” will be displayed.
  4.  Use the Up or Down Arrow keys to change the value of that program.
  5. Press the POWER key to save the new settings, exit the Programming Mode, and return to the Off Mode.

Note: If SMXht is programmed for displaying °C (rather than the factory setting °F), then
functions 3 & 4 should be adjusted. For function 3, the factory setting of 12 (or 1.5°F) should
be changed to 7 (7/8 = 0.8°C). For function 4, the factory setting of 4 (or 0.5°F) should be
changed to 2 (2/8 = 0.3°C). For these functions, 1°F (or 8) = 0.6°C (or 5).