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Troubleshooting a Spa Circuit Board

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The information on this page is for troubleshooting a spa with a printed circuit board (PCB) if you have a mechanical control box (no circuit board) click here

If you are getting any error codes or blinking lights please refer to this Link, for diagnostic help.


Spa Will Not Heat

  • Step 1
    Checking the heating element using a multimeter or ampmeter (see below)


Using a Multi Meter - make sure that the heater/filter cycle is on, and the thermostat is turned all the way up. Using the multi-meter, take one lead from the meter and place it on one of the heater element post. Then take the other lead and place it on the other post. If your spa is operating as a 110 volt system, then this is what you should be reading on the meter, if it is a 220 volt system, then you should be reading 220 volts. Below is the most common element (Flo Thru) used in the industry, however the rules above apply to ALL elements.

Using a Amp Meter - Open the clamp of the amp meter and wrap it around the ONE wire you chose. With the power and heater/filter cycle on, you should be reading approximately 15 amps on a spa that is wired 110 volts, and 25 amps on a spa that has been wired for 220 volts. If you are getting either one of these readings, then the heating element is working properly. Spa water heats at a rate of 3 degrees an hour wired at 110 volts and 10 degrees an hour at 220 volts.

If you did the amp test and had NO reading at all, and then you did the voltage test and HAD THE PROPER reading then the element is defective and will need to be replaced. Find "Heating Elements" in the parts section.

  • Step 2
    When testing the element for voltage or amperage I find no readings (see below)

Shut the power down locate the pressure switch or flow switch pictured above. The pressure switch can be found attached (threaded) to the stainless heater manifold and the flow switch is installed in line with the plumbing Once you have located it, remove both wires that are connected.

Note: Some control boxes with circuit boards do not have pressure switches or flow switches if this is the case then you should either call a local repairman or send the control box to us for repair. Here is what we would need to make the repair/s

TIP: Before removing the wires from a pressure switch spray some WD-40 on the connectors they are attached to, to prevent the fragile micro-switch from breaking. Then, carefully pull them off.

Once they are removed, find some sort of wire to rejoin them but don't do it yet. Turn the power back on, you have 5 seconds to join the wires (bypass) together. Do not join them before you turn the power on. Once you have done this check ACROSS the heater element post, you should have 110 volts or 220 volts depending on what voltage is being supplied to the control box from the house.

Also try it this way if that did not give the readings you're looking for.......turn on the pump and then jump the wires, then test again for voltage across the heating element post.

If bypassing the pressure switch/flow switch allowed the heater to come on, then put the wires back on the switch. Run the spa without the filter, if doing this allows the heater to work then you’ve solved the problem (Replace the Filter). If removing the filter made no difference, then replace the pressure switch. See Pressure Switches and Flow Switches in our parts catalog. Pressure switches and flow switches are the number one cause of "no heat"

If bypassing the pressure switch/flow switch or removing the filter didn't solve the problem, or if you continue to get the FLO error message then most likely there is an issue with the circuit board and it would need to be repaired.  

Other issues that could keep a spa from heating is the temperature sensor, the temperature sensor is a "silver bullet" attached to the gray cable that plugs into the circuit board. The silver bullet is usually housed in the filter area, or in a sensor mount fitting that is mounted in the wall of the spa. In order to get the proper temperature sensor, you would need to Email information about your spa.