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How To Test A HotSprings Heater Relay Board

How To Test Your Heater Relay Board

In this post, we are going to teach you how to test and troubleshoot the heater relay board in your Hotspring Spa’s IQ2020 control box. If your spa is not heating, there is a good chance there could be an issue with the heater relay board. There are just a handful of simple steps needed to figure out the source of the issue. Follow the steps laid out in this post and you will have your answer in no time!

Heater Relay Board Pre-test checklist:

• The red “Power” light on the control panel must be on solid and NOT blinking.
• The green “Ready” light on the control panel should be off.
• The temperature on the control panel must be set higher than what the temperature of the spa water is.
• Have your voltage meter (aka Multi Meter), and a Phillips Screwdriver and needle nose pliers handy.

Testing The Heater Relay Board

IQ2020 Control box

Step 1
Remove the screws from your equipment compartment door and set the door aside.

Step 2
Remove the two small Phillips screws that hold on the front cover of the IQ 2020 Control Box and set the cover aside.

Step 3
Look at the circuit board (motherboard) on the right and make sure that the two LED lights are lit. The green LIM Ok light and the red HTR ON light. It is important that the red HTR ON light is lit before continuing. If it’s not then please contact us.

Step 4
Now turn off the power to your spa. Either unplug it if it’s 120-volt model or turn off the breakers if it’s wired 240 volts.

Step 5
Find where the black and white wire from the heater’s power cord connects onto the front of the heater relay board. The black wire should be connected to the P3 terminal and the white wire onto the P2 terminal.

Step 6
With the power OFF to the spa, gently remove the black wire from the P3 terminal and the white wire from the P2 terminal. If the power is still on to the spa, the board will short out when you remove these wires.

Step 7
Turn the power back on to the spa.

Step 8
Set the voltage meter higher than 300 ACV . Meters vary in design so you’ll need to be familiar with yours. Make sure there is a fresh battery in the meter.

Step 9
Put one probe from your voltage meter onto the P2 terminal and the other probe onto the P3. It won’t matter which probe goes onto the P2 & P3.


My voltage reading was less than 100 volts
If your voltage reading was lower than 100 volts, then the board is damaged and has to be replaced. It is not repairable. Sometimes you can see visible smoke residual between one or more of the black relays (relays are shown above the probes on the Step 9 picture). The 77119 Heater Relay Board is the newest upgraded beefier heater relay board. The original 73355 & 74618 circuit boards were discontinued.

My voltage reading was zero
If you know for sure that you are making a solid connection between the voltage meter probes and the htr board terminals, a voltage reading of zero indicates that the board has failed and needs to be replaced. You can buy a new heater relay board now or Contact us with any questions you may have.

My spa plugs into a 120-volt outlet and the voltage reading was between 110 volts-130 volts.
Your heater relay board is okay but your heater may not be. Contact us so we can walk you through the next steps.

My spa is wired 240 volts and my voltage reading was between 215 volts-250 volts.
Your heater relay board is okay but your heater may not be. Contact us so we can walk you through the next steps.

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Thank you for reading this testing guide from Backyard Plus! If you have any questions about your HotSpring Spa, please don’t hesitate to give us a call! 1-805-541-9000.