Spa & Hot Tub Error Codes – OH, OHH, OHS

Spa & Hot Tub Error Codes – OH, OHH, OHS

In our series on spa and hot tub error codes, today we turn our attention to the HOT messages that your topside control may be trying to give you.

OH, OHH or OHS (overheat) all mean that a temperature sensor has detected unsafe water temperatures of 108° – 118° F, and your spa is in an emergency cool down mode. To dissipate heat, the heater has been turned off and the blower and circulation pumps have been activated.

To allow steam and excess heat to escape, open the spa cover. The spa should be avoided when OHH or OH flashes on the topside control. This could cause the water to be scalding for several minutes. After the water cools down, the high limit switch might need to reset on some spa packages; look out for a red reset key. Press any topside button to reset a digital spa after the water has cooled to 100° F.

What Causes a Spa to Overheat?

A spa or hot tub that has low water flow (LF, FLLO) is usually overheated (OH, OHH). If water doesn’t flow quickly through the heater, it heats up more and causes the water to get hotter. The heater will eventually stop working due to the temperature sensors or high limit switches sensing the higher water temperature. Some causes of low water flow in a spa include:

  • A dirty spa filter cartridge.
  • Valves or jets that are closed or partially closed.
  • Either the pump is locked or has lost its prime.
  • Low water level, the skimmer has stopped sucking air.
  • Spa drain cover or blocked pipe.

What Else Causes a Spa to Overheat?

If your water flow is normal, you may have a problem at the thermostat or high limit switches that were used in older spa packs. They can occasionally become inaccurate or oversensitive. The electronic circuits used in digital spas are much more durable than the mechanical switches. Modern spas will eventually succumb to high limit sensors, temperature sensors, relays, and circuit boards.

Most cases, even for older spas, the water flow problem can usually be fixed quickly and the spa will cool down, restart and restart on its own. You may need to prompt some panels to start up. You may have to manually reset your heater housing’s high limit switch for spas with no digital controls.

Spa Overheating Troubleshooting Flow Chart

Here’s a Cal Spa troubleshooting flow chart that has some other possible triggers of seeing OH, OHS, OHH or HH blinking on your spa panel. After letting the spa cool for 10 minutes, open the spa’s cover. Next, touch the control panel or push the red reset button to turn off air systems.

cal spa OH OHH OHS HH error code troubleshooting chart

A hot tub that is overheating does not necessarily mean it has a problem with the heater. It is almost always due to a flow problem. If it is not a flow issue, it could be a bad temp sensor or high limit switch, or a stuck relay.

Here’s another Cal Spa troubleshooting flowchart for spa error codes OH, including testing the spa heater element for excessive resistance. This type of testing should be performed only with the spa heater turned off and all other systems switched off. Only a qualified person can perform this type of testing.

cal spas OH spa heater code troubleshooting flow chart

You now know what to do if your spa gives you an OH, OHH, or other “overheat error code”. Replace or clean the spa filter. Open all jets and turn on the pump. If the problem persists, you can check your temperature sensor and high limit circuits to make sure there are no wire, plug, or sensor issues.


1. What is an oh code in a hot tub?

An “oh code” refers to the error code that appears on a hot tub’s control panel when there is a problem. The specific error code indicates what system/component needs attention.

2. How can I fix common oh code errors in a hot tub?  

Many oh code errors can be fixed by the homeowner, such as checking/replacing filters, chemicals levels, cleaning jets/inlets, resetting GFCI breakers or control panels, or troubleshooting pump/heating issues.

3. When should I call a hot tub technician for an oh code?

If error codes indicate electrical, component, or system failures, call a professional. Examples include codes for defective sensors, leaks, non-responsive controls, or heating/circulation failures.

4. How long do oh codes typically last before fixing?

Oh codes will remain visible until the underlying problem is resolved. Most minor issues can be fixed immediately. More serious problems may require component replacement and take days to diagnose/repair. 

5. Where can I find my hot tub’s manual for oh code meanings?  

Check your hot tub manual or online manufacturer support for a list of all possible error codes. This will explain what each code indicates and troubleshooting steps to try at home.

Leave a Reply

Your email address will not be published. Required fields are marked *