There are multiple possible causes of a spa not heating – for example: a simple airlock, a faulty heater pump (jet or circulation), a defective circuit board, an electrical issue, a pressure switch or flow switch issue, or a defective heater among other possibilities.
The following technical tips are for testing the heater element and PC board:
The first test that can be performed on the spa heater is testing for “Ohms”.
To do this:
1. Shut off all power to the spa at the breaker and spa pack
2. Remove the wires or copper tabs on the heater element terminals
3. Set your Ohm meter to the lowest setting
4. Place your meter leads on the tip of each element terminal
A reading of 9-14 Ohms is generally good for most heater elements.
The heater and board can also be tested for voltage at the heater and circuit board by doing the following:
With the spa on, test both of the leads on the element at the same time for AC
• If the meter is reading around 240v (or 120V for 120V spas), that means that 240V (or 120V for 120V spas) power is getting “to” the heater from the PC board.
So that would indicate the board is good and likely the system is correctly working to send power to the heater, as needed. This indicates a bad heater, if the spa is not heating and all other components are working.
• If the AC meter is reading zero, the problem is likely with the circuit board, or something in the system that is not allowing the board to send the proper voltage to the heater (pressure switch, flow switch, pump for heater, circ pump for heater)