Temperature Probe (Water Bath Thermistor) - Bunn JDF-2S Service & Repair Manual

SERVICE (CONT.)
Temperature Probe (all Models)
(Also known as Water Bath Thermistor)
FIG. 65 TEMPERATURE PROBE
Location:
The temperature probe is located on the top of the
tank assembly.
Test Procedure:
1. Disconnect the dispenser from the power source.
2. Remove the top rear cover.
3. With a voltmeter, back probe the connector from
the temperature probe.
4. Connect the dispenser to the power source.
5. See the chart for voltage readings.
6. For continuity check, disconnect the dispenser
from the power source.
7. Disconnect the two pin connector from the dis-
penser main wiring harness.
8. With an ohmmeter, check for continuity across
the pins for the black or orange and white wires.
9. See the chart for resistance/voltage readings. Al-
ternate check: Leave two pin connector plugged
in, place dc voltmeter across two pin connector in
parallel, check voltage with dispenser running.
10. Verify wiring to probe.
11. If readings are not present as described, replace
the temperature probe.
NOTE: Some meters have difficulty measuring a sen-
sor either rapidly rising or falling in temperature.
JDF S Bath Thermistor Calibration:
Recalibration of the bath thermistor should be con-
ducted anytime the main circuit board or the bath
thermistor is being replaced.
Recalibration procedure:
Step 1: Remove the front splash panel so you can see
the LED's on the main circuit board.
Step 2: Place the "Program" switch in the "On" posi-
tion. (For early models without the program switch,
place the dispense on/off switch in the "off" position).
Step 3: Remove the thermistor from the bath tank and
place the thermistor in a known 32º F bath or ice wa-
ter. It is very critical that the water must be 32º F, in
order to calibrate the thermistor properly.
Step 4: Push and hold the two left dispense switches
(or both switches on a 2S model). After a few sec-
onds, the green water bath, < 34 LED on the board
will flash slowly.
Step 5: While still holding the dispense switches, tog-
gle the "Program" switch from the "on" position, to
the "off" position, then back to the "on" position. (For
early models without the program switch, toggle the
dispense on/off switch from "off", to "on" and then
back "off" again).
Step 6: The green water bath, < 34 LED on the board
will flash rapidly for a few seconds. When the green
water bath, < 34 LED starts flashing slowly again,
release the dispense buttons. The calibration is now
complete.
Step 7: Place Program switch back in the "off" posi-
tion for normal operation. (or place the dispense on/
off switch back in the "on" position for normal opera-
tion).
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