Slot Machine Error Codes: What They Mean and How to Fix Them

Every slot machine owner will eventually see an error code on their display. The machine locks up, a message appears, and suddenly your evening entertainment is staring back at you with a cryptic code. After 33 years in this business and tens of thousands of tech support calls, I can tell you that about 80 percent of home-use error codes have simple fixes you can handle yourself. Let me walk you through the most common codes by manufacturer.

Understanding Error Codes Generally

Slot machines are computers with extensive self-diagnostic systems. Every time you power on a machine, it runs through a series of checks on its memory, mechanical components, security switches, and peripherals. When something does not pass muster, the machine generates an error code and locks itself to prevent operation until the issue is resolved.

This is actually a feature, not a flaw. In a casino environment, these codes alert technicians to issues before they become expensive problems. In your home, they serve the same purpose but can feel frustrating when you just want to play.

Most errors fall into a few categories: door and security switch errors, hopper and payout errors, bill acceptor problems, memory errors, and communication faults. Knowing which category your error falls into tells you immediately whether it is a quick fix or something requiring technical support.

IGT Error Codes

IGT machines are the most common in home collections, so I will start here. Whether you have an S-Plus, S2000, Game King, or newer IGT cabinet, these codes are consistent across platforms.

Door Open or Door Error

This is the single most common call we get. The machine displays MAIN DOOR OPEN, BELLY DOOR OPEN, or a door switch error even though all doors appear closed.

What it means: Every door on an IGT machine has a magnetic reed switch or microswitch that tells the computer whether the door is open or closed. If the switch is misaligned, dirty, or the magnet has shifted, the machine thinks a door is open.

DIY fix: Open the main door and look along the door frame edge. You will see small switches mounted to the cabinet frame with corresponding magnets on the door itself. Make sure the magnet aligns within a quarter inch of the switch when the door closes. If a switch has physically shifted, loosen its mounting screw, realign it, and retighten. Clean the switch contact area with compressed air. Close the door firmly and turn the jackpot reset key to clear the error.

If the switch itself has failed, a replacement reed switch costs about $8 and takes 10 minutes to swap with a screwdriver.

RAM Cleared or RAM Reset Required

You see CMOS RAM CLEARED or RAM ERROR on the display after a power event.

What it means: The machine's battery-backed memory lost its contents. This happens when the internal lithium battery dies, when there was a power surge, or when the machine was unplugged for an extended period without a healthy battery.

DIY fix: For a simple RAM clear after a power outage, open the main door, locate the jackpot reset key switch, turn it to the reset position, then turn it back. Some IGT models require you to press and hold the service button while resetting. The machine will re-initialize its RAM with default settings.

If this happens repeatedly, the CMOS battery needs replacement. It is a standard CR2032 lithium coin cell on most IGT boards. Pop the old one out, put the new one in observing correct polarity, and the machine will hold its memory through future power outages. Battery costs about $3 at any drugstore.

Hopper Empty or Hopper Error

Displays HOPPER EMPTY, HOPPER JAM, or HOPPER RUNAWAY.

What it means: The coin hopper at the bottom of the machine either has no coins to pay out, has coins jammed in the payout mechanism, or paid out more coins than expected.

DIY fix for hopper empty: If you are running your machine on coin play, simply add coins to the hopper. The hopper holds between 1,000 and 2,500 coins depending on the model. Fill it three-quarters full for best operation. Turn the jackpot reset key to clear the error.

DIY fix for hopper jam: Open the belly door, pull the hopper out (it sits in a cradle and lifts straight up). Look in the payout chute for any coins turned sideways or foreign objects. Coins that are slightly bent or damaged frequently cause jams. Remove the obstruction, replace the hopper, and reset.

Note: If you run your machine on free play mode, hopper errors should never occur because the machine is not attempting to pay coins. If you see hopper errors in free play mode, there may be a configuration issue in the machine's setup menu.

Bill Acceptor Errors

Displays BILL ACCEPTOR ERROR, STACKER FULL, STACKER REMOVED, or BILL JAM.

What it means: The bill validator unit is reporting a problem. These are common because bill acceptors have moving parts and optical sensors that can get dirty.

DIY fix for stacker full: The stacker is the removable cassette that holds accepted bills. Pull it out, empty the bills, replace it. Reset the error.

DIY fix for bill jams: Open the bill acceptor head (it usually hinges open with a thumb latch). Look for paper stuck in the transport path. Gently remove any jammed bill being careful not to tear it and leave fragments inside. Use a bill acceptor cleaning card ($5 for a pack of 10) to clean the optical sensors. Run the cleaning card through three times. This solves 90 percent of bill acceptor issues.

DIY fix for stacker removed: Make sure the stacker cassette is fully seated. It should click into place. If the machine still shows stacker removed, the microswitch that detects the stacker presence may need cleaning or adjustment.

Coin In Meter Error

Displays COIN IN TILT or OPTIC ERROR.

What it means: The coin comparitor or optic sensor that reads coins entering the machine is dirty or malfunctioning.

DIY fix: Locate the coin comparitor in the coin head assembly at the top of the coin chute. Use compressed air to blow out dust. Wipe the optical sensors with a dry lint-free cloth. Do not use liquid cleaners on optical sensors unless they are specifically designed for that purpose. Reset and test with a clean coin.

Bally Error Codes

Bally machines use a slightly different error reporting system. Many Bally errors display as two-digit codes on a seven-segment LED display inside the cabinet rather than on the main screen.

CMOS Error (Bally)

The cabinet LED shows alternating characters or displays CMOS on the VFD.

What it means: Same as IGT RAM errors. The battery-backed memory has been compromised.

DIY fix: Locate the CMOS battery on the main processor board. On most Bally machines from the 1990s and 2000s, this is a 3.6V lithium cell, sometimes soldered in place rather than socketed. If it is socketed, replace it with the correct voltage replacement. If it is soldered, this is a job for someone comfortable with a soldering iron. After battery replacement, you will need to reinitialize the machine using the RAM clear procedure in the operator manual.

Call for help if: The battery is soldered and you are not comfortable with soldering on circuit boards. This is a common repair we handle via our tech support line with step-by-step guidance.

Hopper Errors (Bally)

Bally hopper codes typically show as ERROR 30 through ERROR 39 depending on the specific issue.

Error 30 means hopper empty. Error 31 means hopper jam. Error 32 means hopper runaway, meaning the hopper paid out more coins than it should have.

DIY fix: Same general approach as IGT. Fill the hopper for empty errors, clear jams by removing the hopper and inspecting the payout path, and for runaway errors check that the hopper optic sensor is clean and properly detecting coins as they exit.

Tilt Codes (Bally)

Bally machines have numerous tilt codes that relate to the physical orientation and door security of the machine.

Error 10 through Error 19 are typically door and security switch tilts. Error 10 is usually the main door. Error 11 is the drop door. Error 12 is the top box.

DIY fix: Same approach as IGT door switches. Verify switch alignment, clean contacts, ensure magnets are properly positioned. Reset by turning the jackpot reset key or pressing the attendant reset button depending on your model.

Logic Door Error (Bally)

This is a specific Bally code that indicates the logic compartment (where the CPU board lives) was opened.

DIY fix: Open and close the logic door firmly, ensuring the switch engages. Reset with the attendant key. If you did not intentionally open the logic area, check that vibration has not caused the door to work loose from its latch.

Aristocrat Error Codes

Aristocat machines use alpha-numeric codes that are fairly descriptive. They tend to display the error clearly on the main screen.

RAM Error or Memory Fault (Aristocrat)

Displays MEMORY FAULT or NVRAM ERROR.

What it means: Non-volatile memory has been corrupted, usually from power loss or battery failure.

DIY fix: Aristocrat machines have a RAM clear procedure that typically involves opening the logic door, pressing a specific button combination, and cycling power. The exact sequence varies by model. On MK series machines, hold the service button while powering on to enter diagnostic mode, then select RAM clear from the menu. You will need the attendant and jackpot keys.

Note: RAM clear on an Aristocrat resets all game settings to factory defaults. You may need to reconfigure denomination, payout percentage, and other operator settings afterward.

Door Errors (Aristocrat)

Aristocat displays MAIN DOOR OPEN, LOGIC DOOR OPEN, or CASH DOOR OPEN clearly on screen.

DIY fix: Same principles as other manufacturers. Check switch alignment and magnet placement. Aristocrat uses a combination of reed switches and microswitches depending on the model and door location. The main door switch is typically at the bottom left of the cabinet frame.

Printer Errors (Aristocrat)

Displays PRINTER ERROR, PAPER OUT, or PRINTER DISCONNECTED.

What it means: If your machine has a thermal ticket printer (TITO system), it is reporting a paper or communication fault.

DIY fix: If you do not use the printer for anything (most home users do not), you can often disable it in the operator setup menu, which eliminates these errors entirely. If you want the printer functional, check that the paper roll is loaded correctly with the thermal (shiny) side facing the print head. Check the ribbon cable connection between the printer and the main board.

Communication Errors (Aristocrat)

Displays COMM FAULT or PROTOCOL ERROR.

What it means: The machine is looking for a connection to a casino network or progressive system that does not exist in your home.

DIY fix: Enter the operator setup menu and disable any network communication or SAS protocol settings. The machine does not need network connectivity for home use. Once disabled, these errors will stop appearing. On some models, you may need to set the machine to standalone mode.

Universal Troubleshooting Steps

Regardless of manufacturer, here is a universal approach when you see any error code.

First, write down the exact error message or code. This helps if you need to call tech support.

Second, try the simple reset. Turn the jackpot reset key or press the attendant reset button. Many errors are transient and clear with a simple reset, especially after power events.

Third, power cycle the machine. Turn it off, wait 30 seconds, turn it back on. The reboot process runs all diagnostics fresh and many issues resolve on their own.

Fourth, check all doors and connections. Open each door and close it firmly. Check that all cable connections inside are secure. Vibration from shipping or even from the machine's own speakers can work connectors loose over time.

Fifth, check your environment. Is the room too humid? Is there a new source of electrical interference nearby? Did you recently plug something else into the same circuit?

When to Call for Help

Some issues are beyond DIY regardless of your comfort level with electronics.

Main board failures where the machine shows no display at all or displays garbage characters need professional diagnosis. Power supply failures where the machine will not turn on but has confirmed good wall power should be handled by someone with multimeter experience. EPROM or software corruption where games behave erratically even after RAM clear may require chip replacement. Mechanical reel motor failures on physical reel machines involve precision alignment that is difficult without experience.

Our Free Lifetime Tech Support

Every machine we sell comes with free lifetime technical support. That means you can call us any time you see an error code and we will walk you through the fix. We have seen every code on every machine made in the last 40 years. Most calls take five to ten minutes to resolve.

We also stock replacement parts for every machine we sell. Door switches, batteries, bill acceptor parts, hopper motors, power supplies, and boards are available and ship quickly. About 95 percent of home-use errors can be resolved with a phone call and at most a $10 to $30 part.

Keep your operator keys in a safe place, keep the owner's manual we provide with every machine, and do not hesitate to call when something comes up. That is what we are here for.