IPSO Tumble Dryer Error Code AF-1: Airflow Switch Already Closed
AF-1 on an IPSO 120/170 lb tumble dryer means the airflow switch was found closed before the cycle began, so the control suspects it is stuck or wired wrong. Turn the dryer off and do not bypass the switch. If you ever smell gas, leave the room and call the gas utility from outside.
High: the control withholds heat for safety and the dryer cannot be run until it is fixed.
- Code
- AF-1
- Maker
- IPSO
- Equipment
- Industrial laundry
- Applies to
- Tumble dryers 120/170 lb (TMB1268C family) micro control
What does IPSO error code AF-1 mean?
The airflow switch is a safety device. It is supposed to close only when the blower moves air through the drum and exhaust, which proves there is a path for heat and combustion gases to leave. The micro control checks it before the cycle starts. At that moment the blower is not running, so the switch should be open. If the control finds it already closed, it cannot trust the switch and posts AF-1 rather than allow heat. Plant staff see a dryer that will not begin heating. The causes the manual points to are a switch stuck in the closed position, wiring to it that is crossed or shorted, lint packed around the switch holding it shut, or a switch input on the control that reads closed all the time. Airflow safety matters on gas and steam dryers alike, which is why the answer is never to tape, jam or hold the switch.
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
- Dryer will not start heating
- AF-1 on the display before the cycle
- Drum may tumble but no heat follows
- Code comes back at every start
Possible causes
Listed in IPSO's documentation
- Airflow switch stuck in the closed position
- Wiring to the switch crossed or shorted
- Lint packed around the switch holding it closed
- Switch input on the control that reads closed all the time
Other likely causes — what usually sits behind error code AF-1 on this control. A technician confirms which one it is before any part is replaced.
- A switch vane bent or wedged by lint
- Moisture that corroded the switch contacts
- A harness pinched near the exhaust housing
- A control input that no longer shows open
Safe checks before calling for service
- If you smell gas, leave the room and call the gas utility from outside.
- If there is no odor, turn the dryer off and wait for the drum to stop.
- Never tape, jam or hold the switch to get past the code.
- Call us to test it, and say whether AF-1 shows on every start.
How a technician diagnoses error code AF-1
- Read the code and confirm AF-1 appears with the blower off.
- Inspect the airflow switch and its vane for lint and binding, with power locked out.
- Check switch continuity open and closed by hand.
- Trace the wiring for a short or crossed leads.
- Test the control input; replace the switch or control only after the wiring checks clean.
- The airflow switch protects against unburned gas and exhaust staying in the room, so any bypass is dangerous. The wiring sits near the gas train and live control circuits. Testing it right requires lockout, a meter and knowledge of the dryer's safety sequence.
How error code AF-1 differs from similar codes
This differs from AF-2, where the switch fails to close once the cycle starts, and from a flashing AF, where the switch opens and closes unsteadily.
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
Can I bypass the airflow switch to keep drying?
No. It is a safety device and bypassing it is a hazard.
Will AF-1 clear itself?
It may reset on power-up, but it returns if the switch is stuck.
Is AF-1 a lint problem?
Sometimes. Lint around the switch can hold it closed, but a screen full of lint does not cause AF-1 itself.
Need help with IPSO error code AF-1?
A technician confirms the cause on site and gives you the price in writing before any work starts.