What is wrong? › Commercial HVAC
A stuck economizer pulls in outside air the unit cannot handle
The unit still cools, but it is fighting hot humid outside air all day, and PNNL notes that economizer faults can go unnoticed for a long time while wasting energy and hurting air quality.
What is probably happening
- The economizer is a damper on the rooftop unit that is meant to bring in outside air when it is cool out. When it sticks open in summer, the unit is cooling the outdoors.
- Signs: humid space, a smell of outside air or cooking exhaust, a unit that runs all day, and bills up with no other change.
- A stuck-closed damper is the opposite problem: stuffy air and complaints, with no ventilation coming in.
- Common causes are a failed actuator, a broken linkage, or a bad outdoor air sensor.
Do this in the next five minutes
- Write down when it started. If a service visit or a roof job happened just before, say so.
- Check whether nearby exhaust (kitchen hood, dumpster, generator) sits near the unit's outside air intake.
- Book a visit within the week and ask specifically for an economizer check.
- Ask the technician to show you the damper position at minimum and at full open.
Do not
- Do not let anyone screw the damper fully shut as a fix. Your building still needs outside air for the people in it.
- Do not accept 'it is fine' without a demonstration of the damper moving.
Who to call
A licensed commercial HVAC contractor
Economizer actuators, linkages and sensors are inside the rooftop unit and part of its controls. This is standard commercial HVAC work.
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What it should cost
$100 to $250 per hour plus parts
HVAC labor rate; an actuator or sensor is a parts-and-labor repair
Source: Angi, HVAC repair cost, updated August 2026. View source
National published range, not a quote for your job. The full cost table for this trade is on the commercial hvac page.
Ask this contractor, on the phone, before anyone comes out
Tap each one as you ask it.
- Does the economizer damper move through its full range, and what is the minimum outside air position set to?
- Is the outdoor air sensor or changeover control working, and what does it read now?
- Can you include an economizer check on every maintenance visit and note it on the report?
- Is the outside air intake pulling from anywhere it should not, like a kitchen exhaust?
End the call if
- A suggestion to disconnect the economizer permanently.
- No mention of the damper position on the service report.