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Troubleshooting Hot Tub Circuit Boards

Hot Tub Circuit Board

Troubleshooting Tips For Hot Tubs With A Circuit Board


If your spa does not have a circuit board, click here for mechanical troubleshooting.

Our complete troubleshooting library can be found here.



We repair Hot Tub circuit boards! Click for more information.







Click On A Problem Below To See The Solution:

My 220 Volt Spa No Longer Gets Hot
I'm Getting Error Codes Or Blinking Dots
The GFCI Trips When I Call For Heat Or Turn On The Spa
The Pump Is Coming On By Itself - No Buttons Were Pushed
When I Push A Selected Button, Something Else Comes On
The Display Is Going Wacky And Some Of The Buttons Don't Respond
The Spa Side Buttons Are Not Responding When I Push Them
The Main Terminal Block Where The Incoming Power Terminates Has Burned/Melted
The Copper Straps Connecting The Board To The Heater Have Burned/Melted
One Or More Wires That Connect To The Circuit Board Relays Or Termination Points Have Burned
Bonus! A Few Tips That The Spa Tech Won't Tell You
Topside Error Codes

  • My 220 Volt Spa No Longer Gets Hot

When calling for heat, is the heat indicator light/icon on on the topside control?

Yes, It Is: Measure the voltage across both hot wires coming from the house. You should see 220 volts on your volt meter - note that measuring from each wire to ground will not give an accurate reading). If you DON'T have 220 volts, then you have an issue with the GFCI breaker in the main breaker box. If you DO have 220 volts across both hot wires coming from the house, then next measure the voltage across both heating element pins. You should see 220 volts. If you do not, then the circuit board is faulty and will need to be replaced or sent to us for repair. If you do see 220 volts and it is not heating then the heating element is defective and will need to be replaced.

No, It Is Not: If you are not getting any error messages in the display screen (blinking dots is an error message) then please proceed, otherwise find the steps below to troubleshoot error messages.

In order for the spa to heat, the heat indicator light needs to be on on the topside control. If it is not then there may be an issue with the pressure switch (it may be defective). The pressure switch screws into the heater manifold and has cable leading from the circuit board with two small wires that attach to it; one on each terminal. Use the instructions provided below to bypass the pressure switch to see if it is the cause of the "no heat". Note that not all spas have a pressure switch, so these instructions may not apply.

  1. Power the circuit board down, then unplug the pressure switch cable from the circuit board revealing two pins.
  2. Power up the system. As soon as the low/filter pump turns on, jump the two pressure switch pins on the board with alligator clips. Don't worry, you will not get shocked as the pins are low voltage.

Did the heater light come on on the topside control? If so, the pressure switch or the pressure switch cable is defective and should be replaced. If the light did not come on, then the circuit board will need to be sent in for repair or replaced.

More information regarding "Spa Won't Heat"

  • I'm Getting Error Codes Or Blinking Dots

There are several different error codes that are used by many different manufacturers. The predominant manufacturers are Balboa, Gecko and Hydro Quip. The error code that we are going to look at here is "FLO" or 3 blinking dots. Both mean the same thing and will be troubleshot the same. All other error codes can be viewed here.

"FLO", "FL" and 3 blinking dots mean the same thing - the water flow through the heater is inadequate or the pressure switch is miscalibrated and/or possibly defective. Before we troubleshoot this error code here are a few possible causes:

  1. Dirty filter (remove it)
  2. Too many jets closed off or all jets not installed
  3. Debris wrapped around the pump impeller
  4. Defective pressure switch
  5. Defective pressure switch cable
  6. Defective circuit board

Before proceeding make absolutely sure that the pump which circulates water through the heater is passing water through the heater and also make sure you see water movement in the spa! If you don't confirm water is moving in the hot tub and through the heater do not proceed with the next step as in doing so may burn out the heating element.

To check to see if the pressure switch is defective or miscalibrated, please do the following:

  1. Power down the circuit board. Unplug the pressure switch cable from the circuit board, thus revealing two pins.
  2. Power up the system. As soon as the low/filter pump turns on, jump the two pressure switch pins on the board with alligator clips. Don't worry, you will not get shocked as the pins are low voltage.

Did the error code go away? If so, the pressure switch or the pressure switch cable is defective and should be replaced. If the code did not go away then the circuit board will need to be replaced or sent in for repair.

Back to "if the code did go away after jumping the two pins on the board" - There is a possibility that the pressure switch simply needs to be calibrated. To do this, either turn the wheel or the screwdriver slot on the pressure switch counter-clockwise one full turn (two at the most). If this does not make the code go away, then send the board in for repair or replace it. See complete list of error codes here.

More information regarding pressure switch adjustment.

  • The GFCI Trips When I Call For Heat Or Turn On The Hot Tub

The number one cause for GFCI trips is a shorted heating element. The quickest way to confirm if this is the case is to disconnect both leads from the circuit board supplying power to the heating element. Power up the system again. If the GFCI does not trip, the heating element is shorted and needs to be replaced.

Click to view heating elements.

If the GFCI still trips with the heating element disconnected, then start unplugging one thing at a time from the control box, unplugging the main heat pump last. Turn the power back on each time something is unplugged. If the GFCI holds, then you have found the cause of the GFCI tripping. It will need to be replaced. If you have everything unplugged (including the main pump) and it still trips, then there may be an issue with the transformer that is soldered or plugged into the circuit board. If the transformer plugs into the board it can be easily replaced. If the transformer is soldered onto the board, the board will need to be replaced or sent in for repair.

Click for more information regarding the transformer and how to test it.

NOTE: If this is a new installation and your GFCI is tripping, make sure that the GFCI was installed correctly. Licensed electricians have been known to install GFCI breakers incorrectly. Please refer to this link to confirm that it was wired properly. Click to see GFCI load center wiring examples.

  • The Pump Is Coming On By Itself - No Buttons Were Pushed

The issue is most likely a faulty topside control. Unplug it from the circuit board. If the pump or any other device no longer comes on by itself, then the topside control is faulty and needs to be replaced.

  • When I Do Push A Selected Button, Something Else Comes On

The issue is most likely a faulty topside control by moisture entering the topside. The topside control will need to be replaced.

  • The Display Is Going Wacky And Some Of The Buttons Don't Respond

The issue is most likely a faulty topside control. However, if the circuit board processor/EPROM or power driver is failing, then the issue could be a faulty circuit board. You may want to consider sending the circuit board and topside control to us for evaluation/repair.

  • The Spa Side Buttons Are Not Responding When I Push Them

The issue is most likely a faulty topside control. Make sure that a rodent has not chewed through the cable.

NOTE: When you unplug the topside control from the circuit board, the low speed/filter speed should come on in approximately one minute. If it does not, then either the pump or the circuit board is faulty. Be sure you have proper voltage to the control box from the house and that you also checked each fuse on the circuit board with a meter. Visual checks are not adequate.

  • The Main Terminal Block Where The Incoming Power Terminates Has Burned/Melted
  • The Copper Straps Connecting The Board To The Heater Have Burned/Melted
  • One Or More Wires That Connect To The Circuit Board Relays Or Termination Points Have Burned

All the above were caused by a loose connection. If this is a new installation, the nut/screw were not secured tightly enough, thus creating resistance and heat. If this is an original installation, then vibration may have caused the nut/screw to become loose over time creating resistance/heat.

Please note that if this is a new installation, the manufacturer does not consider this type of damage a manufacturer defect and will not cover it under warranty. It is very important that you make sure all nuts, screws and terminations are sufficiently tight before powering up the system.

We repair circuit boards! For more information click here.

  • A Few Tips That The Hot Tub Tech Won't Tell You

1. Balboa M7 Circuit Board: The reading across the two pins where both the "A" & "B" sensor plug in should read .5 volts DC.

2. Gecko Circuit Board: If you have three flashing dots on the display and there is a red light illuminated on the circuit board then the high limit sensor needs to be replaced. If the red light is not on, then there is a flow issue or faulty pressure switch. See "error codes/blinking dots" above.

3. With the power off and everything hooked up properly, you should get approximately 20 ohms when measuring across line one (L1) and the neutral line with a 120 volt transformer, and approximately 40 ohms with a 220 volt transformer. If you do not get these readings, then either a fuse is blown or the transformer is faulty. Readings should be taken at the terminal block on the circuit board.

NOTE: A reading from L1 to neutral does not indicate a short. The readings above are normal so please do not send your circuit board in for repair with the above readings.

4. If you or the hot tub technician installs a new circuit board and days or weeks later it melts and/or burns at the heater connection, this is due to a loose connection and not a defective board. The manufacturer will not warrant this type of damage. Make sure you sufficiently tighten the heater nut/screw - Torque Specs = 30-35 Inch - lbs.