Service & test modes: Heat Pump tips

Short, practical technician tips on service & test modes for heat pump. Check each one against the manual for your exact model before acting.

Force cooling for charging with the FORCE button

Bosch · BOVA IDS 2.0, IDS Premium Connected and IDS Light heat pumps

A short press of FORCE (SW1) while the unit runs in cooling puts it in forced full-capacity operation for checking charge. On IDS 2.0 the display then shows a bar symbol followed by the compressor frequency.

1. Start the system in cooling mode
2. Short press the FORCE button on the outdoor board
3. Allow about 10 minutes to ramp up and 20 minutes to stabilise before taking charging readings

Read system values with the CHECK button (point check)

Bosch · BOVA IDS Premium Connected (36-60) and IDS Light (BOVA15) heat pumps

Pressing CHECK on the outdoor board steps through system values: each press shows the point number then its value after 1 second. After 20 seconds on a point the display returns to normal. Examples: 0 unit capacity, 1 mode (0 standby, 2 cooling, 3 heating), 2 set compressor speed in Hz, 3 last fault code.

1. Press the CHECK button (SW2) on the control board
2. The point number shows, then its value after 1 second
3. Press CHECK again for the next point
4. Do nothing for 20 seconds to return to the normal display

Run the gateway diagnostic (Factory + Connect buttons)

Bosch · IDS Premium Connected gateway

Holding the Factory button for 3 to 5 seconds puts the gateway in diagnostic mode; Connect then runs a full diagnostic. A fault shows as a red Fault LED blink code.

1. Hold the Factory button for 3 to 5 seconds
2. Press the Connect button to run the full diagnostic
3. Read the Fault LED blink count

Start a manual defrost test (hold FORCE 6 s)

Bosch · BOVA IDS 2.0, IDS Premium Connected and IDS Light heat pumps

Holding FORCE for 6 seconds starts a forced defrost test. The unit must be in a heating call and have run 8 minutes or more. Defrost starts after about 40 seconds and the display shows dF.

1. Make sure there is a heat call and the unit has run 8 minutes or more
2. Press and hold the FORCE button for 6 seconds
3. Wait about 40 seconds; the display shows dF
4. For a second test wait 5 minutes and repeat

Force a defrost cycle by shorting the defrost pins

Carrier · Carrier single-stage communicating heat pump; HK32EA003/008 defrost boards

Starts a defrost by hand. A full defrost only runs with coil at 32 F / 0 C or colder and outdoor air under 50 F / 10 C; otherwise only an abbreviated 30-second defrost. On HK32EA003/008 boards, with the defrost thermostat open you get about 30 s, closed a full cycle.

1. Short the two-pin FORCED DEFROST header for 5 seconds, then release
2. On HK32EA003/008 boards, short the speed-up pins (J1) with a screwdriver for 5 seconds and release
3. On the Infinity single-stage communicating heat pump the same can be commanded from the user interface

Recall the active status code on the outdoor board (25VNA8/24VNA9)

Carrier · Carrier Infinity 25VNA8/24VNA9

Replays the most recent, highest-priority active status code on the amber STATUS LED; codes are kept without power. The unit does not heat or cool while the forced defrost pins are shorted.

1. Turn the unit power OFF
2. Short the FORCED DEFROST connector (J2 on the board) with a clip wire
3. Turn power ON; the amber LED flashes the stored code (short flashes = first digit, long flashes = second digit)
4. Power down and remove the short

Start a forced cooling test run from the indoor unit

Fujitsu · Fujitsu ductless heat pumps: Fujitsu wall-mounted 7-15 (NA ASU/AOU type); Fujitsu ductless heat pumps: Fujitsu multi-zone outdoor 18/24 type (18 type 2-zone, 24 type 3-zone)

Holding MANUAL AUTO on the indoor unit starts forced cooling when the remote is lost or the outdoor unit will not start on room temperature.

1. Keep MANUAL AUTO pressed longer than 10 seconds.
2. Watch for the OPERATION and TIMER lamps flashing together.
3. In the wall unit the heating test run follows about three minutes later when HEAT is chosen on the remote.
4. Stop with the remote START/STOP key, or press MANUAL AUTO briefly.

Start a test run from the wired remote

Fujitsu · Fujitsu ductless heat pumps: Fujitsu wall-mounted 7-15 (NA ASU/AOU type)

Optional wired remote starts the test run with a two-key press while the unit is stopped.

1. Stop the air conditioner.
2. Press the master control key and the fan control key together for 2 seconds or more.
3. Press START/STOP to end the test run.

Force a defrost cycle from the remote

Gree · Vireo GEN3 9-24k (3VIR..HP115/230V1A)

A key sequence on the remote forces the unit into defrost; the unit finishes and returns to normal heating by itself. If a fault or protection stop is active, the sequence only works once that is cleared.

1. Turn the unit on in heating mode and set 16°C.
2. Within 5 seconds press + - + - + - on the remote.
3. The unit finishes the defrost and returns to normal heating by itself.

Force a defrost from the outdoor board (function n3)

Gree · Gree GMV6 Ultra Heat Mini VRF 36-60k (GMV-V..WL/C-T(U))

Forces a defrost during maintenance; the system leaves it on its own when the normal exit conditions are met.

1. Open the function menu: power the system, then hold SW1 on the master outdoor board for over 5 seconds.
2. Pick the function with SW1 (up) and SW2 (down), confirm with SW3.
3. SW4 steps back or exits; with no key pressed for 5 minutes the board leaves the menu by itself.
4. Select n3 (00 flashes) and press SW3; n3 goes steady.

Show indoor engineering numbers on the indoor units (function n8)

Gree · Gree GMV6 Ultra Heat Mini VRF 36-60k (GMV-V..WL/C-T(U))

Every indoor unit shows its engineering number so units can be matched to addresses; operation is not affected.

1. Hold SW2 on the master for over 5 seconds, select n8, confirm with SW3.
2. Hold SW4 on the master for over 5 seconds to return indoor units to normal.

Start pump-down (refrigerant recycle) mode, function A2

Gree · Gree GMV6 Ultra Heat Mini VRF 36-60k (GMV-V..WL/C-T(U))

Pull refrigerant from a faulty module or the indoor pipework into the outdoor unit; the liquid service valve must be closed.

1. Open the function menu: power the system, then hold SW1 on the master outdoor board for over 5 seconds.
2. Pick the function with SW1 (up) and SW2 (down), confirm with SW3.
3. SW4 steps back or exits; with no key pressed for 5 minutes the board leaves the menu by itself.
4. Select A2; the default 01 flashes. Choose the recycle mode with SW1 and SW2, confirm with SW3 (01 recycles the indoor unit pipework).
5. When the display asks for manual recycle, press SW3 on the master; the whole system stops at once and cannot restart for 10 minutes.

Start vacuum mode for evacuating pipework (function A8)

Gree · Gree GMV6 Ultra Heat Mini VRF 36-60k (GMV-V..WL/C-T(U))

Opens every indoor and outdoor expansion and solenoid valve so the whole system can be evacuated; the system cannot be started while A8 is steady. It ends by itself after 24 hours.

1. Open the function menu: power the system, then hold SW1 on the master outdoor board for over 5 seconds.
2. Pick the function with SW1 (up) and SW2 (down), confirm with SW3.
3. SW4 steps back or exits; with no key pressed for 5 minutes the board leaves the menu by itself.
4. Select A8 (00 flashes), then press SW3; A8 goes steady.
5. To leave, hold SW4 on the master for over 5 seconds. The mode also ends by itself after 24 hours.

Force a defrost with the SPEEDUP pins

ICP · ICP N4H3 heat pumps

With the unit heating and the defrost thermostat closed, shorting the SPEEDUP pins forces a defrost. Outdoor fan stops and strip heat comes on during defrost.

1. Run the unit in heating with the defrost thermostat closed (or jumper the DFT terminals)
2. Short the SPEEDUP pins with a screwdriver until the reversing valve shifts
3. Remove the short at once for a brief defrost, or keep it for 2+ seconds to go straight back to heating

Force a defrost cycle or skip the 5-minute delay

KeepRite · Communicating *SA/*SH and *CA/*CH heat pump outdoor boards

Shorting the 2-pin FORCED DEFROST header for 5 seconds on a non-communicating system starts a defrost (communicating systems start it from the wall control). Full defrost if coil is 32 F or colder and outdoor air under 50 F; otherwise a short 30-second defrost.

1. Make sure the system is running a heating call
2. Short the two FORCED DEFROST pins with a screwdriver for 5 seconds, then release
3. To skip only the 5-minute start delay, short the pins briefly and release
4. Quiet Shift compressor on/off delays are included in a forced defrost when enabled

Speed up the defrost timer for testing (J1 speed-up pins)

KeepRite · N4H4/R4H4/WCH4/NXH5 heat pumps; older split heat pump defrost boards

Shorting the J1 speed-up pins shortens the defrost timing. On Quiet Shift-2 boards hold about 5 seconds and release; defrost thermostat open gives only a short defrost, closed a full cycle.

1. Put the unit in heating and let the coil frost (defrost thermostat must be closed for a full cycle)
2. Short the J1 speed-up pins with a flat screwdriver for about 5 seconds, then release as soon as the reversing valve changes position
3. The unit stays in defrost for the remaining cycle time or until the defrost thermostat reopens
4. After the test reconnect anything you disconnected

Force a defrost cycle from the remote

Kinghome · Kinghome KM09HEDI, KM12HEDI, KM18HEDI wall mini-splits; Kinghome KM09HT1DI, KM12HT1DI, KM18HT1DI, KM24HT1DI wall mini-splits

A key sequence on the remote forces the unit into defrost; the unit leaves it by itself when the outdoor unit finishes.

1. Turn the unit on in heating mode and set 16°C.
2. Within 5 seconds press + - + - + - on the remote.
3. The unit exits the forced defrost by itself when the outdoor unit finishes.

Force a defrost from the outdoor board (debug item 06)

Kinghome · Kinghome Ultranixx cold-climate KU36UHO and KU60UHO outdoor units with KU..UH2I and KD..UHI air handlers

Item 06 turns forced defrost on (ON) or off (OF).

1. Hold SW1 about 5 s, short-press SW1 until 06 shows.
2. SW2 or SW3 chooses ON or OF.
3. Short-press SW1 to save.

Force cooling or heating from the outdoor board (debug item 09)

Kinghome · Kinghome Ultranixx cold-climate KU36UHO and KU60UHO outdoor units with KU..UH2I and KD..UHI air handlers

Item 09 forces the system to run regardless of the thermostat: 01 forced cooling, 02 forced heating, OF stops it.

1. Hold SW1 about 5 s, short-press SW1 until 09 shows.
2. SW2 or SW3 chooses 01 (cool), 02 (heat) or OF (off).
3. Short-press SW1 to save.

Start refrigerant recovery from the outdoor board (debug item 08)

Kinghome · Kinghome Ultranixx cold-climate KU36UHO and KU60UHO outdoor units with KU..UH2I and KD..UHI air handlers

Item 08 switches refrigerant recovery (pump-down) on (ON) or off (OF).

1. Hold SW1 about 5 s, short-press SW1 until 08 shows.
2. SW2 or SW3 chooses ON or OF.
3. Short-press SW1 to save.

Start the pilot (test) run from the remote

Kinghome · Kinghome KM09HEDI, KM12HEDI, KM18HEDI wall mini-splits

Runs the unit in cooling and shows dd on the indoor display while the pilot run is active.

1. Cooling mode, set temperature 30°C.
2. Within 3 seconds press + - + - + - on the remote.
3. End the pilot run to clear dd.

Use the defrost control TEST pins to clear lockouts or force defrost

Lennox · Lennox EL16KP1 (Elite) and ML14KP1 (Merit) R-454B heat pumps, sizes -018 to -060, demand defrost control A108 (CMC1)

A jumper on the TEST pins (P1) clears short cycle and five-strike lockouts and forces the unit into and out of defrost; the 30 s defrost off-delay does not work while it is fitted.

1. Place the jumper on the TEST pins of P1.
2. Use it to clear the lockout or to cycle the unit in or out of defrost.
3. After testing, move the jumper back across the desired defrost termination temperature pins (factory setting 50 F).

Start a test run from the wireless remote

Mitsubishi · Mr. Slim PEAD-RP JA(L) ducted indoor units with PAR-21MAA wired remote

Checks cooling and heating without waiting for a thermostat call; FAN, DRY and AUTO cannot be run in test run.

1. Power the unit at least 12 hours ahead of the test run.
2. Start with the remote display off; press the TEST RUN button twice in a row.
3. Press MODE to select COOL and confirm cold air; press MODE again for HEAT and confirm warm air.
4. Press FAN to check the fan speed changes and VANE to check the auto vane moves.
5. Press ON/OFF to stop the test run.

Bypass the 3-minute timer and clear a lockout with TEST (PRL-JEC)

Rheem · Rheem/Ruud PRL-JEC heat pumps with Comfort Control2 ICC

Pressing TEST resets any active-protection lockout and the 3-minute anti-short-cycle timer, and energizes the unit even without a call. Use an insulated probe.

1. Use an insulated probe to press TEST for one second, then let go
2. With a call present the compressor and outdoor fan start and the display settles on c, C, h or H
3. With no call a steady t shows and the compressor runs about 5 seconds

Force a defrost test (PRL-JEC)

Rheem · Rheem/Ruud PRL-JEC heat pumps with Comfort Control2 ICC

With the unit running in heat-pump mode, SW2 forces a defrost that runs until the termination temperature is reached or 14 minutes pass.

1. Set the thermostat to heat and make a heat call
2. Press SW2 for one second with the unit running in heat-pump mode
3. Watch the unit enter defrost; press SW2 again to stop the test early

Review or clear stored faults on the ICC display (PRL-JEC)

Rheem · Rheem/Ruud PRL-JEC heat pumps with Comfort Control2 ICC

Scrolls the stored fault history on the dual display, newest first; up to six are kept and 0 means none. The mode exits by itself after the last fault.

1. Press TEST and SW2 together with insulated probes for one second and release
2. Watch the display scroll through the faults, newest first
3. To erase, hold TEST and SW2 together for five seconds and release; the top and bottom segments flash to confirm

Force a defrost cycle with the button

Trane · 5TWR7 multi-speed outdoor drive

Holding the forced defrost button on the control board starts a defrost; the display then shows 7 as the first digit (Defrosting). Not possible in cooling.

1. Run the unit in heating mode with the thermostat calling
2. Hold the forced defrost button on the control board down for over 5 seconds
3. The display shows 7 as the first digit when forced defrost begins