Johnson Controls T-4000-3139 Plastic Cover the BT1256502 fan relay is

the BT1256502 fan relay is a frequent failure point due to pitted contacts or a failed coil

you can replace a 110V

the SPDT (Single Pole Double Throw) action allows you to toggle power between two different fan speed taps or between a humidifier and a blower

Precise 210°F Setpoint: Fixed temperature calibration prevents drifting

Whether you are performing a seasonal tune-up or a specific burner assembly repair

Johnson Controls T-4000-3139 Plastic Cover the BT1256502 fan relay isThe Johnson Controls T 4000 3139 is a professional grade horizontal pneumatic thermostat cover designed specifically for the T 4000 Series room thermostats. Engineered for demanding commercial environments, this white plastic cover provides a clean, uniform look for horizontal mounted controllers where a blank faceplate cover is required. As a genuine Johnson Controls replacement part, it ensures a precise fit for single or dual element sensing units