Service manual
06/2010
head of air leaving nothing for the water to compress against, leaving the system as if no
accumulator tank had been installed. A good accumulator tank will smooth the pulses and make the
diaphragm pump a stream as smooth as if it were on city water.
4.5 T-in, T-mid, T-out Thermister and T-set readout
If the red LED is flashing, turn power OFF for 5 seconds and then turn power ON? If the red LED is
flashing, there is a potential problem with a thermister.
To diagnose the problem, run water though the unit for at least 30 seconds with the power OFF then
turn the water off. The output of the thermister should be checked with the power ON using a
multimeter. Plug the ground (-) probe into the black test connector (TP1) on the circuit board
1841-RV and the high (+) probe into:
T-out orange test connector (TP2)
T-mid yellow test connector (TP3)
T-in 6 pin connector on 1841-RV at right (inboard) blue wire
T-set blue test connector (TP4)
Compare the voltage reading of the three thermister outputs which should all be within .5 volts of
each other.
Turn power OFF. Unplug the 2-pin connectors (figure -4) and, using a multimeter, check the
resistance across the each thermister. If the suspect thermister is more than 75 ohms from the other
thermisters, replace the thermister. Otherwise, replace the thermister cable (1329) first. If that does
not fix the problem, replace the thermister.
T-set is set to 2.0 vdc (120F) at the factory. The T-set pot output will change about 0.44 vdc (7F)
per turn of the pot. For example, to adjust T-set to 122F turn the pot until the readout is 2.0 vdc.
Section 5. Service Code Diagnostics
Note: All red LED flashes can be reset by cycling the power OFF for 5 seconds and then ON.
Double red flash/second (two flashes per second)
Indicates that the T-mid thermister has failed. The heater will not operate without maintenance
action. Check that the 2-pin and 6-pin connectors are all plugged in and inspect the wiring for any
indications of a problem. Unplug the T-mid thermister 2008 at the 2-pin connector and check the