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10.4.6
Water Pressure Switch
If the meter shows at least a 220mV signal at test
point 11, move the black lead of the meter to the other
terminal on the water pressure switch (test point 12).
If there is no voltage, the pressure switch contacts
are open. This is almost always due to a water flow
deficiency, the most common one being a blocked
water filter or defective pump. However, sometimes it
is due to blockage of the copper siphon loop tube or
mis-adjustment of the switch. Investigate thoroughly,
referring to Section 7.5 on “Water Pressure Switch
Adjustment”. If there is no problem with the pool
system or pressure switch adjustment, replace the
pressure switch.
10.4.7
Temperature Control Circuit
The temperature control circuit consists of four
major components which must all be working cor-
rectly for the signal to be transmitted to the gas valve.
The four components are the ON/OFF toggle switch,
the variable temperature control (potentiometer), the
temperature sensor (thermistor) and the temperature
control board. Use the following procedure to check
each component for functionality.
Check the temperature control as a complete
circuit before checking each component individually.
With the red lead of the meter still at test point 1,
place the black lead of the meter on the TH terminal of
the temperature control circuit board (test point 16). If
the meter shows more than 220mV at the pressure
switch (test point 12) but not at test point 16, then one
of the components of the temperature control circuit is
faulty. Proceed with the following sections to test the
components.
10.4.7.1 ON/OFF Toggle Switch
Remove the temperature control panel from the
bezel on the front of the heater to gain access to the
switch. Be sure that the toggle switch is in the "ON"
position. Place the black lead of the meter on the
toggle switch terminal (test point 13) that is connected
to the pressure switch. Less than 220mV at this point
indicates that there is a problem with the black wire
that connects the pressure switch to the toggle switch.
If at least 220mV is detected at test point 13, move the
black meter lead to the other terminal on the toggle
switch (test point 14). A reading of less than 220mV
here indicates a faulty switch. If the reading is more
than 500mV, turn the switch "OFF" and then "ON"
again to be sure that the internal contacts are working
correctly. The volt meter reading should drop to zero
when the switch is "OFF" and return to at least 220mV
when the switch is placed back in the "ON" position.
10.4.7.2 Variable Temperature Control
The variable temperature control is a 0-10,000
ohm variable resistor. Set your ohmmeter to the 0-20K
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range. Remove the temperature control wires from
the control circuit board. Place one lead of the meter
on each of the wires (test points 18 & 19). With the
control set to MIN the meter should read near 10,000
ohms. Now turn the control to the MAX position. The
meter should read close to zero. If the meter shows an
open circuit, or readings outside of the range stated
above, replace the controller. If the control is working
correctly, reconnect the wires to the circuit board.
10.4.7.3 Temperature Sensor
The temperature sensor is a 0-20,000 ohm
thermistor. Set your ohmmeter to the 0-20K range.
The meter readings will depend on the temperature of
the water in the header. See the chart below for
approximate readings at various temperatures.
To test the temperature sensor, circulate water
through the heater for 5 minutes. Remove the tempera-
ture sensor wires from the temperature control board.
Place one lead of the meter on each wire of the
temperature sensor (test points 20 & 21). Record the
reading. Measure and record the water temperature of
the pool near the inlet of the filter system. Find the
temperature in the chart that is closest to your tem-
perature reading of the pool water. Compare your
ohmmeter reading to the resistance number in the
chart. Remember that this is an approximate reading
and numbers may vary. If your reading is close to the
numbers indicated in the chart then the temperature
sensor is working correctly. Reconnect the wires to the
circuit board. If your reading is vastly different or
outside of the ranges shown the temperature sensor
should be replaced.
10.4.7.4 Temperature Control Circuit
Board
With the red lead of the meter still at test point 1,
place the black lead of the meter on the TH/PP termi-
nal of the temperature control circuit board (test point
15). If there is more than 220mVDC at this point but
not at the TH terminal of the temperature control
circuit board (test point 16) as tested in section 10.4.7,
then the control circuit board is faulty. Replace the
board.
