EVCO AL06

What does EVCO AL06 mean?

AL06 on the Evco SAVE AHU controller (144SAVEU0E01) indicates that the outside air damper has failed to reach its fully open or fully closed limit switch position. The controller monitors the damper end-position limit switch and triggers AL06 when the switch contact is open at a point where the damper should be at its commanded limit. The controller shuts all AHU devices down in response and requires a manual reset from the operator.

Symptoms

• AL06 displayed on the SAVE AHU controller.
• All AHU outputs are switched off — fan, heating, and cooling disabled.
• Outside air damper is not confirming its commanded end position.
• Limit switch contact is open when it should be closed for the current damper position.
• Alarm requires manual operator reset after the damper issue is corrected.

Common causes

• Damper actuator has failed or lost power, leaving the damper blade stuck between positions.
• Damper blade mechanism is jammed by ice, debris, or a seized shaft bearing.
• Limit switch on the damper assembly has failed or is misaligned with the blade.
• Actuator control wiring to the controller is broken or has a loose connection.
• Damper blade is manually locked in an intermediate position from previous service work.

Diagnostic steps

1. 01

   Locate the outside air damper and actuator

   Identify the outside air damper assembly in the AHU inlet section. Confirm the actuator is receiving the correct control signal voltage from the SAVE controller output.

2. 02

   Check damper blade position and blade freedom

   Observe the actual damper blade position. If the actuator is powered but the blade is not moving, the blade shaft may be seized or an obstruction is present. Remove any ice or debris and manually verify the blade pivots freely on its shaft.

3. 03

   Inspect the limit switch and its alignment

   Locate the end-position limit switch on the damper frame. With the actuator at full travel, confirm the switch cam engages the switch plunger. Adjust the switch position if the cam is misaligned; replace the switch if it fails to conduct when physically actuated.

4. 04

   Check actuator and control wiring

   Test actuator output voltage at the controller terminals and verify wiring continuity to the actuator. A broken wire or loose terminal prevents the actuator from receiving its control signal. Replace actuator if it has failed.

5. 05

   Perform manual reset and confirm damper operation

   After repairing the damper, access the controller alarm menu and manually reset AL06. Power up the AHU and observe the damper driving to its startup position. Confirm the limit switch makes contact and AL06 does not return.

When to call a professional

Call a licensed HVAC technician if the damper actuator requires replacement — commercial actuators are wired into the AHU controls system and may require re-commissioning for spring-return timing and control signal calibration. If the damper is inaccessible due to AHU location or requires scaffold access, the repair should be carried out by a qualified technician with appropriate access equipment.