Dexter Commercial Washer Error Codes F6 and F7: Comm Error 3
F6 and F7 (COMM ERROR 3) mean the washer size or type configuration changed, or the jumper harness configuration is invalid. Power the washer off for a minute and on again, and note any recent controller, drive or harness work. Do not unplug harnesses yourself; call us.
Medium: the washer will not run, but the likely cause is a harness or setting rather than a failed part.
What does Dexter error code F6 / F7 mean?
The controller on a Dexter VFD washer expects the harness to describe a valid washer. Through the jumpers in that harness it learns the size and type, and it checks these against what it last knew. If the configuration has changed since the previous start, or if the combination of jumpers does not describe any real washer, the controller stops and shows F6 or F7 (COMM ERROR 3). It is a configuration error rather than a communication loss, although the name suggests otherwise. The maker lists the harness connections, the drive size for the washer, and an odd but specific item: the orange wire from the pressure switch. That wire is part of the harness the controller reads, so a pressure switch connector that is loose or a wire that is damaged can make the configuration look invalid. As with the other configuration messages on these washers, the code often turns up after a controller or drive replacement, when a part from a different washer or a different harness has been fitted.
Affected models and control systems
Dexter C-Series and T-series coin washers with a VFD, T-300 to T-1450, such as the T-650 Express.
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
- F6 or F7 appears and the washer will not start
- The message came after a controller, drive or harness change
- The washer powers up but refuses every cycle
- The code stays through repeated restarts
Possible causes
Listed in Dexter's documentation
- Invalid harness connections or jumper settings
- Drive size that does not suit the washer
- Damaged orange wire from the pressure switch
- Controller or drive recently replaced
Other likely causes — what usually sits behind error code F6 / F7 on this control. A technician confirms which one it is before any part is replaced.
- A pressure switch plug that was disturbed when the tub or hoses were serviced
- A harness from a different washer type fitted during a repair
Safe checks before calling for service
- Switch the washer off for a minute and on again.
- Note any recent controller, drive or harness work.
- Do not unplug harnesses yourself.
- Call us to schedule service and give us the model number.
- Tell us what changed before the message first appeared.
How a technician diagnoses error code F6 / F7
- Confirm which of F6 or F7 is shown and read the model number.
- Compare the harness jumper configuration with the correct pattern for the washer.
- Check the orange wire at the pressure switch and its connector for damage and seating.
- Confirm the drive size matches the washer.
- Reseat or correct the harness, then run a cycle to confirm both codes stay clear.
- Harness and jumper settings are read by the controller as the washer's identity, so a wrong guess can stop it running.
- The orange pressure switch wire is part of that harness and is found inside the cabinet.
- Checking the drive size against the washer takes the model number and the maker's data.
How error code F6 / F7 differs from similar codes
F5 (COMM ERROR 2) concerns the washer size jumpers; F6 and F7 (COMM ERROR 3) cover a changed or invalid harness configuration.
Technical reference
- Document
- Dexter Common Washer Troubleshooting and Error Codes (Washer Fault Errors, pp. 4-10)
- Maker documentation
- Dexter owner support
- Edition
- Part # 8533-***-*** 9/19
- Models / control
- Dexter C-Series and T-series coin washers with VFD (T-300 to T-1450)
- Section
- Washer Fault Errors & Codes, printed pp. 4-10 (PDF pp. 5-11); contents on p. 1
- 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 Dexter washer error codes
Why are F6 and F7 on one page?
The maker gives them the same meaning, COMM ERROR 3, so the checks are the same.
Does the pressure switch really matter here?
Yes. The maker names its orange wire, which forms part of the harness the controller reads.
Will a restart clear it?
Not if the configuration is actually invalid. The controller repeats the same check.
Need help with Dexter error code F6 / F7?
A technician confirms the cause on site and gives you the price in writing before any work starts.