Bunn Axiom coffee brewer Error Codes
Applies to: Axiom and Infusion Series ICB digital-control brewers. Compiled and paraphrased from the Bunn-O-Matic Axiom Service and Repair Manual, document 39132.0000G, covering the Axiom family and the digital brewer control used across several Bunn ranges. Resistance and temperature figures are Bunn's published values. Confirm against the manual for your model. Extended from Bunn's own Infusion Series documentation, including service and programming manuals published on bunn.com and its qr.bunn.com document service, which supplies the three messages that BLOCK a brew before it starts (BREW TEMPERATURE TOO LOW, CHECK FUNNEL, SERVER NOT IN PLACE), the brew lockout behaviour and its roughly 25-minute heat-up, the electronic funnel lock, the service access route and advanced password, and the 20 to 90 psi operating water pressure range. Those three messages are deliberate refusals rather than faults, which is why they are recorded here as such. Table last updated Aug 22, 2026.
How to read the codes
Bunn's digital brewers show WORDS rather than numbered codes, on two lines: a message and a prompt. The striking thing about the list is how much of it is one problem. THREE OF BUNN'S DIAGNOSTIC MESSAGES SAY DIFFERENT THINGS ABOUT THE SAME CAUSE, which is lime, and their remedy for all three is identical: clean the sprayhead, the brew valve and the tank. If your water is hard and you are not descaling, this is the page you will keep coming back to.
The codes
| Code | Meaning | Likely causes | Operator-safe steps | Technician work |
|---|---|---|---|---|
| CHECK SPRAYHEAD FOR LIME / CHECK FITTINGS FOR LIME | The control has detected flow consistent with scale building up | Lime in the sprayhead, the brew valve, or the tank | This is the earliest of the three lime warnings and the cheapest to act on. Clean the sprayhead. Bunn is explicit that a clean sprayhead is required for proper extraction, so ignoring this costs you coffee quality before it costs you a repair | Delime sprayhead, brew valve and tank. Inspect the dispense valve for deposits |
| WARNING INACCURATE FLOW / TOO MUCH LIME PLEASE REPAIR | Scale has progressed far enough that brew volume is no longer reliable | Lime in the sprayhead, brew valve or tank | Same cause as the first message, further along. Descaling now is still cheaper than a valve | Full delime. Volume adjustments must be made with the sprayhead installed |
| WARNING VERY LOW FLOW / PLEASE REPAIR | The last of the three lime warnings; flow is now badly restricted | Lime in the sprayhead, brew valve or tank | By this point a technician is likely needed. Worth telling them your water hardness, because a brewer that limes up repeatedly is a water treatment problem rather than a brewer problem | Delime; consider whether treatment is needed upstream |
| Temperature Too Low | Tank water has not reached ready temperature | The brewer is simply still heating, or brew lockout is holding it | Usually not a fault. Wait for it to heat. Bunn's own remedy also allows disabling the BREW LOCKOUT feature, but that means brewing below temperature, and water below 195F at the sprayhead will not extract properly | If it persists, check tank heater, limit thermostat and TCO |
| Heating Time Too Long | The tank is heating but not getting there | Tank heater failure, or a control board or thermistor failure | Report it rather than working around it. A brewer that cannot reach temperature is producing under-extracted coffee, not just slow coffee | Tank heater resistance against Bunn's chart, then temperature probe: roughly 4VDC cool to 1VDC at ready, or 10.5k ohms cool to 870 ohms at ready |
| Fill Time Too Long | The tank is taking too long to refill | Water shut off, supply line too small or obstructed, inlet solenoid failure, control board failure, or simply the ON/OFF switch left off | Check the water is on and nothing upstream is closed. Bunn lists the switch being off among the causes, so check that too before calling | Refill valve coil voltage and continuity, then supply line and control board |
| Temp Sensor Out Of Range, Check For Bad Connections | The temperature sensor circuit reads open | Temperature sensor probe open, or a disconnected lead | No operator action | Check the probe at J9; open reads out of range. Replace probe if resistance is off spec, replace the board if it is not |
| Temp Sensor Out Of Range, Check Wire For Shorts | The temperature sensor circuit reads shorted | Temperature sensor probe wires shorted | No operator action | Trace the probe harness for a short before condemning the probe |
| Brew starts, then aborts and returns to the main screen after 20 seconds | The brew abort feature has triggered because the water level did not drop as expected | Mineral build-up on the level probes or grommets, probes shorting to the top cover with the mylar shield missing, a plugged outlet such as a limed sprayhead, or on pour-over models an operator pouring water in AND pressing start | On a pour-over model, use one method or the other, not both. Bunn names this explicitly as a cause, which means it happens often enough to document | Clean probes and grommets, confirm the mylar shields are fitted, delime the sprayhead. Probe reading around 255 means not grounded, 0 to 2 means grounded |
| FACTORY BLOWOUT on the display | A factory-only mode was entered by pressing both hidden switches together | Accidental entry during programming | Not an operator screen | Bunn's warning is emphatic: NEVER activate this mode, because it opens the brew and refill valves simultaneously. Exit by pressing the ENABLE BREW ON/OFF switch |
| BREW TEMPERATURE TOO LOW | The brewer is refusing to start because the tank is below its ready temperature | Not a fault. This is BREW LOCKOUT, a deliberate feature that blocks brewing until the water reaches the programmed READY TEMP, so nobody serves under-extracted coffee from a cold tank. It appears most often first thing in the morning, after a refill, or after the brewer has been switched off | Bunn's own remedies, in order: wait for it to heat, or cancel the brew lockout option if you accept the consequence. From cold, allow about TWENTY-FIVE MINUTES for the tank to reach temperature. Water dripping from the funnels during that heat-up is expansion and is normal | If it never clears, treat it as the temperature faults below rather than as a lockout problem. READY TEMP is adjustable in programming |
| CHECK FUNNEL | The brewer will not start because the funnel is not right | Another deliberate block rather than a fault. The brewer has detected that the funnel is missing, not seated, or still holds the previous batch of grounds | Remove the funnel, empty the old grounds and filter, and replace with fresh. Note the ELECTRONIC FUNNEL LOCK on Infusion Series brewers will not release the funnel until drip-through is complete, so a funnel that will not come out is the machine protecting you from a scald, not a jam | Persistent CHECK FUNNEL with a correctly seated funnel points at the funnel sensor or, on Smart Funnel models, the read coils |
| SERVER NOT IN PLACE | The brewer will not start because it cannot see a server under the funnel | Third of the three messages that stop a brew before it begins, and the one most often read as a failure. The brewer is refusing to pour hot coffee onto the drip tray | Put a server under the brew funnel. Bunn also notes a brew should only ever be started with an EMPTY server, since beverage left from a previous batch is a common cause of an overflow that then gets reported as a volume fault | A server correctly in place that still reports missing points at the server switch or sensor |
| Getting into service access, and the password | Not a fault: how to reach the settings behind these messages | Bunn's published route on Infusion Series brewers is to TOUCH THE BUNN LOGO FOR TWO SECONDS to enter service access. The advanced menu behind it takes the password 7738. Worth recording because an operator watching a technician do this often assumes something is broken that requires a code | Not an operator procedure, but knowing it exists saves a call when a setting has simply been changed | Restoring factory defaults replaces ALL previously entered values including recipes, though it does not reset the life brew counter. Note the settings before you do it |
| Water pressure outside 20 to 90 psi | A supply problem that presents as brewer faults | Bunn specifies operating water pressure between 20 and 90 psi (138 to 620 kPa). Outside that range the symptoms are inconsistent beverage level, long fill times and volume faults, none of which look like a plumbing problem from the front of the machine | If several unrelated faults appeared at once, or after work was done on the building plumbing, mention the water supply when you call | Check operating pressure before condemning the fill valve or the control. Also check the inlet strainer, where the flow arrow must point TOWARDS the brewer |
If this needs a coffee brewer technician
8 companies in this directory name Bunn on their own site: that page shows who has been phone-confirmed, who publishes 24/7 cover, and what each puts in writing. Start there if the brand matters more than the city.
Two questions worth reading before you ring anyone: what to do first when a code appears and how to tell whether it is yours to fix.
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Related: the PM checklist that prevents the most common codes outright, and the operator guides for symptom-first diagnosis.
Not sure this is the right make? The lookup by code shows every make that uses a given code, and flags the ones that mean different things depending on the machine in front of you.