Safety: Unplug the unit before opening the control compartment or touching compressor wiring.

Steps:

Listen for compressor: When powered, if the compressor never attempts to start and E9 is displayed, suspect the control/relay.
Inspect wiring: At the compressor, verify that the harness is intact and the plug is firmly seated on the compressor terminals.
Access control board: Remove the control cover and locate the compressor relay on the PCB (often a small rectangular component with 3–5 pins).
Check for damage: Look for burn marks or cracked solder joints around the relay. Gently wiggle the relay to see if it is loose.
Board-level repair: In most home settings, the entire Transtherm main control board is replaced rather than the individual relay. Order the correct board for your model.
Install new board: Label and transfer all connectors one by one to the new board, mount it securely, and reassemble the cover.
Test: Restore power and verify that the compressor now starts and E9 is cleared.

Warning: Do not bypass the compressor relay or hard-wire the compressor; this is unsafe and can cause fire or compressor damage.

Display shows E9 and the cabinet does not cool; compressor may not start

Possible Causes