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Power Light Flashing on Your Spa’s Control Panel? Follow These 9 Steps!

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In this post, we will teach you exactly what to do if the power light on your HotSpring Spa’s control panel is flashing. You may need a couple of basic tools for this tutorial depending on your situation.

control panel

Troubleshooting Overview

When the power light on the control panel of your spa is flashing, it means the high limit sensor has tripped. On most occasions, this is caused by a faulty high-limit sensor but in 1997-2002 spas, without a pressure switch, the flashing power light could be due to poor water circulation because of dirty/clogged filters, air-locks, or a bad circulation pump. On less common occasions there can be an issue with the circuit board, control head, Multicolor LED light, or the heater

Tools Needed:

  • Standard Phillips Screwdriver
  • Voltage Meter

SAFETY FIRST: Turn off the main power to the spa before following any of the steps below.

Step 1

Remove the Spa Filters

Access the filter cartridges in the filter compartment. Remove the filter cartridge with the grey cap. If none of your filters have a grey cap, just remove all of the filters. After the main filter has been removed, Power on the spa.

If the power light on the control panel stops flashing, you need to clean or replace your spa filters.

If the power light keeps flashing, move on to step two.

Step 2

Remove any Air-Locks

If you started experiencing the “power light flashing” issue right after draining and refilling your spa, you may have an air-lock in your system. To clear an air-lock our of your system you will need to follow these steps:

  • Turn off power to the spa
  • Remove the main filter in your spa (usually has a grey cap)
  • Remove the filter standpipe
  • Put a garden hose down the plumbing fitting that leads the circulation pump (use a rag to seal around the hose)
  • Turn the water on full blast and let it run for at least 2 minutes
  • Restore power to the spa

You may notice bubbles coming from different areas in the spa. If you do see this it is likely that you had an air-lock.

If this still didn’t do the trick, try this next step.

Step 3

Check the Circulation Pump

First, you will need to open the spa equipment compartment and locate the circulation pump. Next, check to see if the circulation pump is running. You can place your hand on the pump and you should feel a slight vibration. You should also hear a humming sound. If you know your circulation pump is running, move on to step 4.

If your circulation pump is not running, turn off the power to the spa and open the spa’s control box. Once opened, restore power to the spa. You are going to want to check the voltage where the circulation pump plugs into the board:

  • Set your voltage meter to ACV (200)
  • Place one probe on the terminal of the white Circ Pump wire plugs in and the other probe on the terminal where the black Circ Pump wire plugs in.
  • If your Circ pump has a fuse on the black wire, make sure to test the black wire on the Circ pump (outgoing) side of the fuse. If you have no power on the black wire going to the circ pump, you probably have a blown fuse. Replace the fuse.

If you are getting a voltage reading around 120v, then you will need to replace your Circulation Pump.

If you are not getting the proper voltage (near 110v-120v), you will need to double-check that the “Summer Timer” mode is not enabled. If the Summer Timer mode is off and your fuse is good, you will need to replace the main motherboard.

Step 4

Check Control Panel and LED Spa Light

In this step, we will inspect the LED lights on the motherboard. If the “Control Unplugged” LED is lit, you may have to replace the control head (or on some occasions a bad Multicolor LED Spa Light will be the issue). To check the spa light, disconnect the power from the spa. Next, unplug the two spa light connectors from the Multicolor LED spa light port and the I2C interface port. Reconnect power to the spa. If the power light stops flashing it means you have a bad Multicolor LED spa light. It must be replaced.

If only the “LIM OK” LED is lit, you will want to move on to the next step.

Step 5

Check the Spa Heater

Locate your spa’s heater. Run your hand along the outlet side of the metal heater tube. If you notice a spot on the metal tube that is extremely hot, you are most likely dealing with a bad heater.

If the heater isn’t too hot to touch, move on to the next step.

Step 6

Check High Limit and Control Thermistors

Are your thermistors plugged in correctly? Most of the time, if you just replaced the thermistors, the reason for the flashing power light is that the thermistors are plugged in wrong. Check the connections again. If the connectors are off by one pin it will cause the power light to flash and nothing will work.

If the thermistors are new and are plugged in correctly, you can skip to the next step. If your thermistors are old and your power light is flashing, it is possible that the high-limit thermistor has gone bad. It’s time to check the kOhms of your thermistors. For instructions on checking the kOhms on your thermistors.

Test Procedure
1. Set the meter to 20K on the OHM scale.
2. Record the temperature of the spa water.
3. Unplug the thermistor from the control box.
4. Meter across the two Thermistor leads.
5. Refer to the Temperature versus Resistance chart below to find the correct resistance value for the temperature measured. If the temperature and resistance does not match that of the chart, this test has failed and the thermistor must be replaced. Remember if the spa has been inactive, the spa water temperature may be different than the water temperature in the heater housing.

thermistor resistance chart 2-

Click this chart to show the OHM range of the thermistor
Note: ALWAYS REPLACE THE THERMISTORS IN PAIRS. If a new thermistor differs in temperature sensing more than five degrees from the old thermistor, the system will go into a “fault mode” and prevent the heater, jet pump(s) and light from operating. So again, when replacing a control thermostat thermistor always replace the high limit thermistor as well and vice versa.

Step 7

Cold Water Startup

If the water temperature is below 55 degrees or above 118 degrees the power light will flash. Get a digital thermometer and measure the water temperature. If you have another set of sensors, place them in a cup of warm water to trick the tub into thinking that the water is warm. If you don’t have extra sensors you can use a hair dryer for 5-10 minutes near where the sensors connect to the heater. Now turn the power back on to the spa. It should reset.

Step 8

Voltage Spike

If there was some sort of voltage problem like a lightning strike, a power surge, or if you were running your spa on a generator, it could cause your power light to flash. The power light flashing is most likely a bad motherboard and control head. They must be replaced at the same time.

Final Step

If none of these steps has resolved the flashing Power light Issue, please give our Spa Technicians a call at 805-541-9000.

Thanks for reading “Power Light Flashing on Your Spa’s Control Panel?”

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