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Edward HughesAug 10, 2025
Why is my Johnson Controls Controller OFF?
- NNathaniel MooreAug 10, 2025
If your Johnson Controls Controller is OFF, it might be due to a shorted transformer, a polarity issue with a 24 VAC powered sensor, or a polarity issue with an SA Bus device. First, ensure the polarity of ~24 V COM / UI-C / + 15VC/SA BUS COM on the controller, auxiliary devices, and I/O is consistent. Second, make sure that the BO-1, BO-2, and BO-3 terminals of binary outputs are not connected to ~24 VAC COM, and verify that BO-C terminals are not connected to ~24 VAC HOT, as these terminals are internally sourced. Next, use an ohm-meter to verify that the short circuit has been resolved. Finally, reset the breaker/fuse or replace the transformer, preferably with a model that utilizes a resettable circuit breaker for easier troubleshooting.