Find Why the Economizer Misbehaves
Narrow it to a stuck damper, a bad enthalpy sensor or a binding actuator.
System Diagnostics
Sort Out Rooftop Calls Without Getting Lost in the Wiring Diagram
ACLogics gives you the checks in order for economizers, phase monitors and belt-drive blowers, so you leave the roof with the cause confirmed.
FAULT SYMPTOM
Low suction pressure
CHECK 01
Measure Evaporator Temperature Drop (Delta-T). What is the temperature drop across the coil?
High Drop (Above 22°F)
DIAGNOSIS
Dirty air filter, closed supply registers, or low speed blower.
Low Drop (Below 16°F)
CHECK 02
Measure Superheat and Subcooling. What are your readings?
High Superheat, Low SubcoolingLow Superheat, High Subcooling
Complete diagnostic tree — every branch, every fault path
Try ACLogics Free — iPhone & AndroidWhat You'll Stop Guessing About
Know what failed before you order the part.
Keep the Blower Motor From Burning Up
Check belt tension, sheave alignment and motor amps so the motor doesn't overheat.
Catch Power Problems Before They Kill a Compressor
Check phase balance, spot single-phasing and test the contactor under load.
How a Call Goes
01
Tell It What's on the Roof
Enter size, voltage and heat type (gas or electric), so the checks fit the unit.
02
Check Safeties and Controls in Order
Work through safety circuits, freeze stats and building automation inputs, most likely first.
03
Confirm It's Performing
Check supply air temperature, static pressure and economizer operation before you leave.
Frequently Asked Questions
The economizer stays open when it's hot outside. How do I fix it?
This usually means a failed enthalpy sensor or a stuck actuator. We guide you through testing the sensor resistance and manual positioning.
I hear a squealing noise on startup. Is it the belt?
Likely. It could be a loose belt or a sheave alignment issue. Our guide helps you measure deflection and check for pulley wear.
The unit trips on high pressure but the condenser is clean. Why?
Check for non-condensables, condenser fan rotation (especially on 3-phase), or a restriction. We help isolate the cause systematically.
Know What to Check Next on Your Next Call
Get the checks in order, confirm the cause, and fix it right the first time.