IPSO Tumble Dryer Error Code AF Flashing: Airflow Switch Cycling
A flashing AF on an IPSO 120/170 lb tumble dryer shows that the airflow switch opened and closed five or more times while the dryer ran. Airflow is unsteady, so the control cannot trust it. Stop the dryer and clean the lint screen once it is cool, and if you smell gas, leave the room and phone the gas utility from outside.
Medium: the dryer may keep running with unsteady heat, but the airflow cannot be trusted.
- Code
- AF (flashing)
- Maker
- IPSO
- Equipment
- Industrial laundry
- Applies to
- Tumble dryers 120/170 lb (TMB1268C family) micro control
What does IPSO error code AF mean?
The airflow switch should stay closed all the time the blower is moving air. The micro control counts how often the switch changes state during a run. When it opens and closes five or more times, the control treats the airflow as unreliable and flashes AF. Plant staff see heat that cuts in and out, long dry times, or a dryer that stops. A partly blocked exhaust, a lint-laden screen, wind pressure on the outside vent, or a switch that chatters can all be behind it. The difference from AF-2 is that air is arriving, but not steadily enough to hold the switch closed. Because the air path is a safety matter on gas and steam dryers, the answer is to restore good airflow rather than ignore the flashing. A gas odor near the dryer means walk out and phone the utility from a safe distance.
Affected models and control systems
IPSO 120/170 lb tumble dryers in the TMB1268C family with the micro control. Other controller generations use different codes.
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
- Heat that cuts in and out
- Longer than normal dry times
- Dryer stops partway through the load
Possible causes
Listed in IPSO's documentation
- Exhaust duct and outside hood partly blocked
- Lint screen condition
- The airflow switch and its wiring
- Back pressure and make-up air
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.
- Wind gusts pushing back on the outside hood
- Lint buildup inside a long duct run that varies with load
- A switch vane that sticks and chatters
- Several dryers sharing one exhaust and pulling against each other
Safe checks before calling for service
- If you notice gas, exit the room first and let the utility know from outdoors.
- Otherwise, stop the dryer and clean the lint screen when it is cool.
- Note whether the flashing starts after the dryer has run a while.
- Contact us to check the duct and the switch.
How a technician diagnoses error code AF
- Read the code and confirm AF flashes after a period of running.
- Inspect lint screen, duct and outside hood for partial blockage.
- Check the switch vane and wiring for chatter with power locked out.
- Measure airflow or static pressure in the exhaust.
- Check make-up air and shared duct effects before replacing the switch.
- Exhaust duct work often runs overhead and carries a fire risk from lint. Static pressure measurements need instruments and training. Burner and blower circuits are live and gas-fed, so a wrong adjustment can create a combustion hazard.
How error code AF differs from similar codes
This differs from AF-1, where the switch is closed before start, and AF-2, where it never closes.
Technical reference
- Document
- Tumble Dryers 120/170 lb Troubleshooting TMB1268C, Part No. 70399901R2, Dec 2016 (pp.53, 65)
- 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 IPSO industrial laundry error codes
Is a flashing AF dangerous?
It signals unreliable airflow on a gas or steam dryer, so it should be taken seriously and the dryer checked.
Why only after the dryer has been running?
Lint builds up in the screen and duct as the load dries, which weakens the airflow over time.
Will a bigger vent hood fix it?
Not without a duct check. The cause could be the switch or back pressure.
Need help with IPSO error code AF?
A technician confirms the cause on site and gives you the price in writing before any work starts.