UniMac Commercial Dryer Error Code AF-2: No Airflow Proven
AF-2 means the airflow switch on a UniMac 120 or 170 lb dryer did not close after the cycle started, so the control could not confirm air was moving. Let the drum cool, empty the lint screen and check the outside exhaust opening. If it returns, call us.
High: the burner will not stay lit without proven airflow, so the dryer cannot complete cycles.
What does UniMac error code AF-2 mean?
A gas dryer is only allowed to light its burner once the control sees proof that air is moving through it. After the cycle starts and the blower runs, the airflow switch should close. AF-2 means that never happened, so the control cannot confirm air and the burner will not stay lit. Heavy lint in the exhaust, a blocked exhaust outlet, a weak or backward blower and a switch that does not move are the usual reasons. Because dryers push moist air outdoors, a damp laundry room with little make-up air also makes it harder to draw air through. The control would rather stop the cycle than run hot with no airflow.
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-2 on the display shortly after start
- Burner lighting briefly or not at all
- Clothes damp at the end of a shortened cycle
- Warm air blowing weakly from the exhaust outlet
Possible causes
Listed in UniMac's documentation
- Lint in the exhaust duct and the outlet
- Blower condition and rotation
- Airflow switch and its sensing path
- Make-up air available to the room
Other likely causes — what usually sits behind error code AF-2 on this control. A technician confirms which one it is before any part is replaced.
- An outdoor exhaust damper clogged with lint, so it only opens a crack
- A long or crushed duct run that adds more resistance than the blower can overcome
- A room closed up tight so the dryer starves for air to draw
Safe checks before calling for service
- Turn the dryer off and let the drum cool before you go further.
- Empty the lint screen and look for lint at the door opening.
- Check that the exhaust outlet outside is not covered or packed with lint.
- If gas is ever smelled, go outside and call the gas utility from there. Then call us.
- Note whether it happens on every load or only full ones.
How a technician diagnoses error code AF-2
- Ask how long the duct run is and when it was last cleaned.
- Check the outdoor damper and the duct for lint and crushing.
- Verify the blower runs in the right direction and spins freely.
- With power off, inspect the airflow switch, vane and sensing tube for lint or sticking.
- Check that the room has enough make-up air while the dryer runs.
- Replace the switch or blower only after the airflow and switch tests, then run a full cycle.
- Duct and blower work involves live wiring and a gas burner that must not run without proven airflow.
- Judging blower rotation and airflow resistance needs instruments, not a quick look.
- Bypassing the switch to dry a load is a fire and carbon monoxide risk, so we never do it.
How error code AF-2 differs from similar codes
AF-2 is the opposite of AF-1: here the switch fails to close once air should be moving, whereas AF-1 is a switch that was already closed at start.
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.
Related UniMac dryer error codes
Why does AF-2 only show on full loads?
A heavy load adds lint and moisture, which can tip a marginal duct or blower into failing the airflow check.
Can I run the dryer on a lower heat?
No. The check is for airflow, not temperature, and the control will not light the burner without it.
Is cleaning the duct enough?
Often it is the first fix. If AF-2 stays after a clean duct, the blower or switch is the next place we look.
Need help with UniMac error code AF-2?
A technician confirms the cause on site and gives you the price in writing before any work starts.