While used across many models

reducing electrical arcing and extending the service life of the compressor contactor or fan relay it initiates

check the ohm resistance of the coil

providing ample coverage to conceal footprint marks

Technicians should replace the orifice if the pilot light appears lazy or yellow

Johnson Controls T-4000-2138 Plastic Cover While used across many modelsThe Johnson Controls T 4000 2138 is a professional grade beige plastic thermostat cover designed specifically for T 4000 series pneumatic room thermostats. This field standard component provides a clean, streamlined aesthetic for commercial HVAC systems where tamper resistance and a minimalist profile are required. Engineered for versatility, the T 4000 2138 supports both horizontal and vertical mounting configurations, accommodating various pneumatic