Jacuzzi Z Builder Series Mechanics And Repair page 42

even with the power off, then it's likely the board. What can happen is the heater
relay although closed and apply voltage to the heater, it's not allowing enough
current to reach the heater element. To determine if that is the problem, you need
to test the amperage draw when the heater is on.
What the spa tech will do is use his meter set to AMPS and test one hot wire to
the spa. He will note the amperage draw when the pump comes on. Then when
the board turns on the heater and the heater light is solid he will notice the meter
show a large demand again. If so, the heater should be heating. Yours would not.
But if you don't have a meter to check the amps or do not know how to, if you
have come to this point and can't check the amps, then you should expect the
board to be the cause of the heater failure.
IF the heater light does NOT come on or is flashing, that means there is a failure.
See the "CODES" failure section.
Why do Heaters Fail?
Heaters tend to fail one of two ways. They no longer pass current through the
element and therefore no longer heat.
The most common cause of this failure is water quality. Over time water quality
can cause the element to "leak" current and cause the GFCI to shut down the
spa. The manufacturers of elements insist that if the water is kept to "optimum"
levels that the element should last forever. Their claim is that the only thing that
will harm an element is the on/off of the electrical current to the heater and poor
water quality that damages the element itself.
Their claim is paralleled to a light bulb. If you leave a light on and do not turn if off,
it will last a long time. It's the initial startup that causes the bulb to fail (that's why
this flash when you turn them on). The element on the heater is supposed to have
the same problem. Since they will literally be turned on/off throughout the day
over the years, they fail. That along with the water quality determines the longevity
of the heater.
Therefore you can extend the life of your spa by making sure the top and sides of
the spa are insulated well (to lower heat lost) and keep the water chemistry