Generac Code 1505: RPM Sense Loss and How to Clear It

How to clear Generac code 1505

1505 clears at the panel, and what you do next depends on whether the unit failed to start or was running and stopped. For a failed start, the manual's test is the BATTERY menu: CHECK BATTERY means replace it, GOOD means call a dealer. Clear it with no household load connected; the button sequence for your controller is under clearing a Generac alarm.

What the manual says to do once it is cleared

Both owner's manuals list RPM SENSE LOSS twice in the Quick Reference Guide, and which row applies depends on what the unit was doing. If it would not start, the Guardian manual (p. 34) says:

Clear alarm. Using control panel, check battery by navigating to BATTERY MENU option from MAIN MENU. If battery condition displays GOOD, contact an IASD. If control panel displays CHECK BATTERY, replace battery.

The Next Generation manual (p. 37), for a controller with no display: "Check battery condition in Mobile Link or Field Pro app. Contact an IASD if battery condition shows good."

If it was running and shut down, the Guardian manual (p. 34):

Clear alarm and remove household loads from generator. Put into AUTO and restart. If generator does not start, contact an IASD.

The Next Generation row (p. 37) is the same except that it reads "Put back in AUTO and restart."

If 1505 won't clear, or comes back

Generac's RPM sense article: "If issues persist after performing the checks and attempting to restart, contact a Generac IASD for diagnosis." Its warning for the restart: "Never start a generator while under load." The checks it means are listed further down, under what Generac says you may check yourself.

What code 1505 means

Generac's support article defines the whole family in one sentence: "The controller does not detect a valid RPM signal during startup or has lost a valid RPM signal while running." Codes 1500 through 1522 all carry the display name RPM SENSE LOSS, and the Mobile Link message for the family reads "The generator has experienced a no crank RPM Sensor alarm. Please contact a dealer."

Generac does not publish, in any owner-facing document, what distinguishes 1505 from its neighbors 1501, 1511 and 1515. Those distinctions exist in Generac's dealer service literature, which is not public and which this site does not cite. What the owner's manual does distinguish is the situation: it gives one instruction for RPM SENSE LOSS that occurred during cranking and a different one for RPM SENSE LOSS that occurred while running. You know which happened — the unit either never started, or it started and then stopped — and that, not the number, decides what you do next.

Owner checks Generac lists for RPM sense loss

That list is complete. It does not include listening to the engine, opening the enclosure to inspect the starter or ignition coils, or forcing an automatic transfer by cutting utility power — none of those are Generac owner procedures, and the starter and ignition system are where the dealer's diagnosis begins.

Battery and filter numbers behind a 1505

The battery row is the only one an owner acts on for this code. Starter motors and ignition coils are engine-specific and Generac publishes no owner-facing part number for them; the dealer pulls the right one from your serial number. Match the battery to your unit's generation, not to a kilowatt range — the Next Generation line takes a different battery from the Guardian, and the battery page keeps that scope.

When RPM sense loss needs a dealer

Codes and symptoms near 1505

1100 Overcrank is the code you see when the engine cranks its full cycle and never starts; it and 1505 often appear together on a unit with a weak battery. If the display is dark rather than showing a code, that is the control panel fuse or the battery, not this family — see Generac won't start. If the unit will not respond at all and the shutdown switch has been touched, see 2800. Every code, with its reset: Generac error codes.