How to diagnose a non-working spa and hot tub heater (115v systems)

Posted by on 6/23/2023 to Heater

**Danger Live Electricity**

This step will require working with live electricity and the use of an electrical multimeter with Amp Clamp. If you are unfamiliar with or have no experiencing dealing with electricity, please consider contacting a professional service technician to perform this diagnosis.

Follow these steps to diagnose your non-working spa heater with your 115V systems:

Step 1

Verify that the pump that pushes water through the heater is running normally.

Fig. 1: Displaying temperature normally (no errors) on the keypad screen

Step 2

On the keypad, verify that there are no errors codes or obvious issues being displayed on the screen. (Fig.1)

Step 3

On the keypad, verify that a call for heat is being shown. (Usually, an indicator light or heat icon) (Fig.2)

Fig. 2: Indicator light on the spa keypad screen signifies Call for Heat

Step 4

With a multimeter set to “AC Voltage”, Verify good incoming power to terminal block from main breaker (108v-132v) (Fig.3)

Fig. 3: Test voltage on spa control system circuit board (115v)

Step 5

With multimeter set to “AC Voltage”, Verify proper voltage to the heating element. Place one probe on one of the heater terminals and the other to Neutral or Ground. (108v-132v) (Fig.4)

Fig. 4: Test voltage to spa heater element (115v)

Step 6

Be sure only the circulation or pump #1 low speed is engaged. (No other pumps or blowers)

Step 7

With multimeter set to “Amperage”, use clamp on the meter and place around the main “Hot” incoming power wires from breaker. (Fig.5) (Only clamp around the Hot wire (usually black), never multiple wires at once, and never ground or neutral)

Fig. 5: Testing Amp draw on spa control system circuit board (115v)

Step 8

Verify power being drawn by the system. (Amp draw will indicate total power being drawn on the system). Low amp draw (3-5) amps will indicate only the pump amps are being measured. High amp draw (13-16) amps will indicate both the heater and the pump are being measured.

Step 9

With proper power at main terminal block, but no power going to the heating element, a problem with the control system / circuit board is indicated. Contact a trained service technician or replace circuit board or control system.

Step 10

With Proper power going to the element, but low amp draw, a bad element is indicated. Contact a trained service technician or replace heating element (if possible) or entire heater assembly.