UniMac Commercial Dryer Error Code AF Flashing: Airflow Unsteady
A flashing AF on a UniMac 120 or 170 lb dryer means the airflow switch opened and closed 5 or more times in one cycle. Turn the dryer off, let it cool, clean the lint screen and check the outside exhaust opening. Call us if it returns.
High: the control cuts out the burner when airflow is unsteady, so the dryer will not finish cycles reliably.
What does UniMac error code AF mean?
This version of the airflow code is about instability, not absence. The control watches the airflow switch while the burner is on. In a healthy dryer the switch closes when air flows and stays closed. When air through the dryer pulses, the switch keeps changing state. Once the control counts 5 or more openings and closings in one running cycle, it cuts out the burner and flashes AF. The air may be pulsing because lint is building in the exhaust, because the outlet is partly blocked and opening and shutting with the wind, or because a weak blower cannot keep a steady flow. A switch with a bad contact can chatter even when the air is steady. Since a flickering safety input cannot be trusted, the control stops heat instead of running through it.
Affected models and control systems
This applies to UniMac 120 and 170 lb tumble dryers with the On Premise Micro control, such as the UA120L, in the TMB1268C troubleshooting family.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- AF flashing on the display
- Burner cutting out and relighting during a cycle
- Cycle stopping partway through a load
- Clicking from the airflow switch area
Possible causes
Listed in UniMac's documentation
- Lint buildup in the exhaust duct and outlet
- Blower condition
- Airflow switch contacts
- Wiring at the airflow switch
Other likely causes — what usually sits behind error code AF on this control. A technician confirms which one it is before any part is replaced.
- An outdoor damper that flutters open and shut in gusty wind
- A blower wheel with lint caked on its blades, which lets air surge
- A loose switch connector that makes contact only when the cabinet vibrates
Safe checks before calling for service
- Turn the dryer off and give the drum time to cool.
- Clean the lint screen thoroughly.
- Check that the outside exhaust opening can open freely and is not clogged.
- If you smell gas, leave at once and phone the gas utility from outdoors. Then call us.
- Note how far into the cycle the flashing begins.
How a technician diagnoses error code AF
- Ask when in the cycle AF begins and whether the burner cycled before it.
- Inspect and clear the duct and outdoor damper, checking that the damper moves freely.
- With power off, check the blower wheel for lint and the shaft for play.
- Test the airflow switch contacts with a meter while moving the vane by hand.
- Check the switch wiring for loose terminals that could chatter.
- Replace the failing part, then run a full cycle watching the burner.
- A burner that keeps relighting on an unsteady safety input is a gas-handling hazard.
- Blower and switch checks happen inside the cabinet near live wiring.
- Finding an intermittent contact needs a meter and patience, and a quick reset only hides it.
How error code AF differs from similar codes
A flashing AF counts repeated switch changes in one cycle, while AF-1 and AF-2 are single-state conditions seen at start or after start-up.
Technical reference
- Document
- Tumble Dryers 120/170 lb Troubleshooting TMB1268C, Part No. 70399901R2, Dec 2016 (pp.53, 65)
- Maker documentation
- UniMac owner support
- Edition
- Part No. 70399901R2, December 2016; models through serial no. 0907000048
- Models / control
- Tumble dryers 120/170 lb (TMB1268C family) micro control
- Section
- Hybrid Timer Control Troubleshooting - 31. Error Codes, printed p. 53 (PDF p. 55); On Premise Micro Control (RM) Troubleshooting - 36. Error Codes, printed p. 65 (PDF p. 67)
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
What does flashing mean here?
The airflow switch changed state 5 or more times in one running cycle, so the airflow is not steady.
Is this more serious than AF-2?
Not necessarily. It points to unsteady air or a chattering switch rather than no air, but the dryer still stops heating.
Will a long cooldown clear it?
Restarting may let it run a while. If lint or the switch is the cause, it will flash again.
Need help with UniMac error code AF?
A technician confirms the cause on site and gives you the price in writing before any work starts.