Summary:

This compressor circuit troubleshooting guide applies to the Precedent and Foundation with the Symbio 700 unit controller. The following images illustrate the circuit route for the auxiliary and safety components to the contactor, ensuring the compressor circuit is correctly connected and closed.

Compressor Proving Troubleshooting

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-J8-1 (BL wire), then to 
  • PPM72/PPF72-3 (BL wire), then to
  • PPF2/PPM2-1 (BL wire), then to
  • TNS2 (Transformer)

Compressor 1 Run Command - Resistance 

• What is the resistance between UC-P8-5 and AB-J5-9?

  • Place a meter on resistance (Ω). One lead on UC-P8-5 (Y wire) and the other lead on AB-J5-9 (O/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 = (R wires)
    • AB-J13-3 = (BL wire)
    • AB-J13-2  = (R wire)
    • HCP1 = (R wires)
    • AB-J13-1 = (BK wire)
    • AB-J20-5 = (Y wire)

• What is the resistance between AB-J5-9 and AB-J5-10?

  • Verify AB-J5-9 (O/BK wire) and AB-J5-10 (Y/BK 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.
    • PPF81 = (O/BK pin 9) or (Y/BK pin 10)
    • PPM81 = (O/BK pin 9) or (Y/BK pin 10)
    • PPF23 = (O/BK pin 1) or (Y/BK pin 2)
    • PPM23 = (BK pin 1) or (BK pin 2)
    • CC1 = (BK wires)

Revision C

Revision E

Path: J20-4 > UC-J8-4 > UC-J8-5 >J20-5 > Test Pin Comp 1 Run > J13-1 > BK HPC1 > R HPC1 > J13-2 > Test Pin HPC1 > J13-3 > BL DTL1 > O DTL1 > J13-4 > Test Pin DLT1 > J5-9 > O/BK CC1 > Y/BK CC1 > J5-10

Compressor 1 - Auxiliary 

• Does UC-P8-2 have 24VAC?

  • With the unit powered up, there should be 24 VAC from UC-P8-2 to the (R wire) on CC1 AUX1.
  • Once the Contactor (CC1) closes, the auxiliary closes, and it sends 24VAC 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 UC-P8-2 (R wire), and close the contactor. The resistance should not exceed 0.6 ohms.

Revision C

Revision E

Path: UC-J8-2 > J20-2 > Test Pin TNS > J5-5 > Y/BK CC1 > O/BK CC1 > J5-6 > Test Pin Comp1 Prov > J20-3 > UC-J8-3

Compressor 2 Run Command- 24VAC

• Does UC-P9-4 have 24VAC?

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

• Is there no 24VAC on UC-P9-4?

  • Verify that the Adapter Board AB-J20-4 (Y/BK wire) is powered by 24VAC. If no voltage is present, backtrack to the connector below.
  • AB-J8-1 (BL wire), then to 
  • PPM72/PPF72-3 (BL wire), then to
  • PPF2/PPM2-1 (BL wire), then to
  • TNS2 (Transformer)

I

Compressor 2 Run Command - Resistance 

• What is the resistance between UC-P9-5 and AB-J5-11?

  • Place a meter on resistance (Ω). One lead on UC-P9-5 (BR wire) and the other lead on AB-J5-11 (BR/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 (BR wire) to.
    • AB-J11-4 = (O wire)
    • DTL2 = (R wires)
    • AB-J11-3 = (BL wire)
    • AB-J11-2  = (R wire)
    • HCP2 = (R wires)
    • AB-J11-1 = (BK wire)
    • AB-J20-11 = (BR wire)

• What is the resistance between AB-J5-11 and AB-J5-12?

  • Verify AB-J5-11 (BR/BK wire) and AB-J5-12 (BK/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.
    • PPF81 = (BR/BK pin 9) or (BK/R pin 10)
    • PPM81 = (BR/BK pin 9) or (BK/R pin 10)
    • PPF24 = (BR/BK pin 1) or (BK/R pin 2)
    • PPM23 = (BK pin 1) or (BK pin 2)
    • CC2 = (BK wires)

Revision C without Test Pins

Revision E with Test Pins

Path: J20-10 > UC-J9-4 > J20-11  > Test Pin Comp2 Run > J11-1 > BK HPC2 > R HPC2 > J11-2 > Test Pin HPC2 > J11-3 > BL DLT2 > R DLT2 > J11-4 > Test Pin DLT2 > J5-11 > BR/BK CC2 > BK/R CC2 > J5-12

Compressor 2 - Auxiliary

• Does UC-P9-2 have 24VAC?

  • With the unit powered up, there should be 24 VAC from UC-P9-2 (BL/BK wire) to the (R/BK wire) on CC2 AUX2.
  • Once the Contactor (CC2) closes, the auxiliary closes, and it sends 24VAC to UC-P9-3 (O/BK 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 UC-P9-2 (BL/BK wire), and close the contactor. The resistance should not exceed 0.6 ohms.

Revision C without Test Pins

Revision E with Test Pins

Path: UC-J9-2 > J20-8 > Test Pin TNS > J5-7 > R/BK CC2 > BL/BK CC2 > J5-8 > Test Pin Comp2 Prov > J20-9 > UC-J9-3

Relay Contact Resistance Test

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.

Compressor Proving Alarms

Possible Alarms:

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.

*Advanced. License is not applicable to Foundation Products

Current Precedent and Foundation Adapter Board with Relay Protection and Test Pins.

For Odyssey units - Symbio™ 700 - Compressor Proving Circuit(s) Troubleshooting for Odyssey – Trane Commercial HVAC Help Center

WARNING:

Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.