Symbio™ 700 - Compressor Proving Circuit(s) Troubleshooting for Odyssey

Adapter Board Revision

You can find the REV number on the top right-hand side og the adapter board.

Rev E, before the 5th week of 2026

No test pins

Rev F after the 5th week of 2026

Revision F board has test pins.

Compressor 1 Run Command - 24VAC

Does UC-P8-4 have 24VAC?

• Verify that UC-P8-4 (O wire) to chassis ground has 24VAC (There should always be 24VAC when the unit is powered on). That is the 24VAC input.
• If the contactor does not pull in and LED 5 is on for stage two of cooling, you have 5 seconds to verify the 24Vac output from the unit controller (UC-P8-5 (Y wire)) or the circuit.

Is there no 24VAC on UC-P8-4?

• Verify that the Adapter Board AB-J20-4 (O wire) is powered by 24VAC. If no voltage is present, backtrack to the connector below.
• AB-J5-1 (BK wire), then to 
• PPM61/PPF61-1 (BK wire), then to
• TNS1 (Transformer)

Compressor 1 Run Command - Resistance

What is the resistance between UC-P8-5 and AB-J7-1?

• Place a meter on resistance (Ω). One lead on UC-P8-5 (Y wire) and the other lead on AB-J7-1 (BK wire). The resistance should not exceed 0.6 ohms.
• If the resistance is higher than 0.6 ohms, a pin or plug is not fully seated, or a safety sensor has high resistance.
• If there is no resistance (O/L), backtrace the connectors below. One lead on UC-P8-5 (Y wire) to
  • AB-J13-4 = (O wire)
  • DTL1 = (Wires)
  • AB-J13-3 = (BL wire)
  • AB-J13-2  = (R wire)
  • HCP1 = (Wires)
  • AB-J13-1 = (BK wire)

  • AB-J20-5 = (Y wire)

    

What is the resistance between AB-J7-1 and AB-J7-2?

• Verify AB-J7-1 (BK wire) and AB-J7-2 (R wire). There should be 5 to 12 ohms of resistance because you are going through the contactor coil.
• If there is no resistance (O/L), backtrace the connectors below.
  • PPM23 = (BK wire)
  • PPF23 to CC1 = (BK wire one)
  • CC1 to PPF23 = (BK wire Two)

  • PPM23 - (R wire)
     

    

    

Path: J20-4 → UC-J8-4 → UC-P8-5 → J20-5 → Test Pin COMP 1 → J13-1 → BK HPC1 → R HPC1 → J13-2 → Test Pin NET J13_2 → J13-3 → BL DLT1 → O DLT1 → J13-4 → Test Pin HPC_1 → J7-1 → BK CC1 → R CC1 → J7-2

Compressor 1 - Auxiliary 

• Does AB-J5-1 have 24VAC?
  • With the unit powered up, there should be 24 VAC from AB-J5-1 to the AB-J22-1 on CC1 AUX1.
  • Once the Contactor (CC1) closes, the auxiliary closes, and it sends 24VAC to AB--J22-2, then to AB-J20-3, then to UC-P8-3 (BL wire).
• Resistance Test

  • With the unit off, place a meter on resistance (Ω). One lead on UC-P8-3 (BL wire) and the other lead on AB-J5-1 (BK wire), and close the contactor. The resistance should not exceed 0.6 ohms.

    

    

    

Path: J5-1 → J22-1 → BK AUX → R AUX → J22-2 > Test Pin COMP1 PROV → J20-3 → UC-J8-3

Compressor 2 Run Command - 24VAC

Does UC-P9-4 have 24VAC?

• Verify that UC-P9-4 (Y/BK  wire) to chassis ground has 24VAC (There should always be 24VAC when the unit is powered on). That is the 24VAC input.
• If the contactor does not pull in and LED 15 is on for stage two of cooling, you have 5 seconds to verify the 24Vac output from the unit controller (UC-P9-5 (BR/BK wire)) or the circuit.

Is there no 24VAC on UC-P9-4?

• Verify that the Adapter Board AB-J20-10 (Y/BK wire) is powered by 24VAC. If no voltage is present, backtrack to the connector below.
• AB-J5-1 (BK wire), then to
• PPM61/PPF61-1 (BK wire), then to
• TNS1 (Transformer)

Compressor 2 Run Command - Resistance 

• What is the resistance between UC-P9-5 and AB-J7-3?
  • Place a meter on resistance (Ω). One lead on UC-P9-5 (BR/BK wire) and the other lead on AB-J7-3 (BL wire). The resistance should not exceed 0.6 ohms.
  • If the resistance is higher than 0.6 ohms, a pin or plug is not fully seated, or a safety sensor has high resistance.
  • If there is no resistance (O/L), backtrace the connectors below. One lead on UC-P9-5 (BR/BK wire) to
    • AB-J11-4 = (O wire)
    • DTL1 = (Wires)
    • AB-J11-3 = (BL wire)
    • AB-J11-2  = (R wire)
    • HCP1 = (Wires)
    • AB-J11-1 = (BK wire)

    • AB-J20-11 = (Y wire)

      

• What is the resistance between AB-J7-3 and AB-J7-4?
  • Verify AB-J7-3 (BL wire) and AB-J7-4 (O wire). There should be 5 to 12 ohms of resistance because you are going through the contactor coil.
  • If there is no resistance (O/L), backtrace the connectors below.
    • PPM24 = (BL wire)
    • PPF24 to CC2 = (BK wire one)
    • CC2 to PPF24 = (BK wire Two)

    • PPM23 - (O wire)

      

      

Path: J20-10 → UC-J9-4 → UC-J9-5 → J20-11 → J11-1 → BK HPC2 → R HPC2 → J11-2 → Test Pin NET J11_2 → J11-3 → BL DTL2 → O DLT2 → J11-4 →Test Pin HPC_2 → J7-3 → BL CC2 → O CC2 → J7-4

Compressor 2 - Auxiliary 

Does AB-J5-1 have 24VAC?

• With the unit powered up, there should be 24 VAC from AB-J5-1 to the AB-J22-1 on CC1 AUX1.
• Once the Contactor (CC1) closes, the auxiliary closes, and it sends 24VAC to AB--J22-2, then to AB-J20-3, then to UC-P8-3 (BL wire).

Resistance Test

• With the unit off, place a meter on resistance (Ω). One lead on UC-P9-3 (O/BK wire) and the other lead on AB-J5-1 (BK wire), and close the contactor. The resistance should not exceed 0.6 ohms.

  

  

  

Path: J5-1 → J22-3 → BL AUX → O AUX → J22-4 → Test Pin COMP2 PROV → J20-9 → UC-J9-3

Symbio 700 UC P8 CC1 Relay contact resistance check steps

1. Unplug the UC-J8 harness from the Red P8 connection on the board. Pay attention to which pins the Orange (UC-P8-4) and Yellow (UC-P8-5) wires are connected to.
2. Connect to the Symbio 700 UC board with the cell phone app and go to the Tools > Service Test Mode page.
3. Click on Cool 2 to energize the compressor relay output on the Symbio 700 UC. LED 5 on the Symbio 700 UC board should be ON.
4. Check the relay contact resistance across the (UC-P8-4) and (UC-P8-5). You will only have about 5 seconds to check this before getting a proving fault. The resistance should be less than 10 ohms.

5. Repeat this process several times to see if the relay contact ohm reading changes. If the ohm reading exceeds 10 ohms, the Symbio 700 UC board will need to be replaced.

   

   

Symbio 700 UC P9 CC2 Relay contact resistance check steps

1. Unplug the UC-J9 harness from the White UC-P9 connection on the board. Pay attention to which pins the Y/BK (UC-P9-4) and BR/BK  (UC-P9-5 ) wires are connected to.
2. Connect to the Symbio 700 UC board with the cell phone app and go to the Tools > Service Test Mode page.
3. Click on Cool 1 to energize the compressor relay output on the Symbio 700 UC. LED 15 on the Symbio 700 UC board should be ON.
4. Check the relay contact resistance across the  (UC-P9-4) and (UC-P9-5). You will only have about 5 seconds to check this before getting a proving fault. The resistance should be less than 10 ohms.

5. Repeat this process several times to see if the relay contact ohm reading changes. If the ohm reading exceeds 10 ohms, the Symbio 700 UC board will need to be replaced.

   

   

Alarm - Compressor Proving Trip Diagnostic – 15-minute lockout

• The HPC or DTL opens while the compressor is running (after the circuit has proved), and the Compressor Contactor loses its 24 VAC, causing the Aux Switch to open

Alarm - Compressor Proving Lockout Diagnostic – INSTANT UNIT LOCKOUT!

• The Symbio Board calls for the Compressor Contactor, and the Contactor doesn’t pull in within 7 seconds.

Possible causes:

The HPC and or the DTL are open.

Contactor Coil open.

Wiring error.

Alarm - Compressor Proving Lockout Diagnostic – INSTANT UNIT LOCKOUT!

• The Symbio Board calls for the Compressor Contactor; it pulls in and drops back out after 7 seconds.

Possible causes:

No 24 VAC at the black wire on the Aux Switch

Bad Aux Switch.

Aux Switch is not on the contactor correctly.

Alarm - Compressor Contactor Fail Diagnostic – INSTANT UNIT LOCKOUT!

• The Compressor Contactor Aux Switch closes before it is supposed to

Possible causes:

• The technician manually pushes in the contactor.
• The contactor welded shut.