Time/Temperature Circuit - Troubleshooting; Water Level Probes; Set Point - Cleveland SteamCraft V Service Manual

Page 64 CET-16 Service Manual

Time/Temperature Circuit - Troubleshooting

WATER LEVEL PROBES

Set Point

Improper cooking cycles may result from a faulty timing circuit, or a
damaged or improperly installed thermostatic switch.
1. To check the timing circuit, locate the two purple wires at CON 2. Trace
these wires back toward the temperature switch and unplug them at
the in-line connectors to the temperature switch. Jumper the two purple
wires together to simulate a closed switch.
2. Start a TIMED cycle and check the countdown on the front panel
display using an accurate watch or clock. A 3-minute test usually
suffices.
• If the timer counts correctly when isolated from the temperature
switch, the switch is either faulty or not property installed. Replace
and/or install the switch properly.
• If timer fails to count minutes correctly when isolated from the
temperature switch, separate the purple wires and check for correct
voltage (12 VDC) between them. If no voltage is detected, inspect
wire leads and terminals and repair as required.
3. To test the thermostatic switch, disconnect switch and jumper wires
(follow step 1 above).
4. Start a TIMED steamer cycle. Using an ohmmeter, check that the
switch closes when compartment temperature reaches 180°to 200°F.
This should occur about the same time as the rear contactor starts to
cycle OFF and ON. After the compartment heats up and the switch
closes, turn the steamer OFF and open the steamer door. The switch
should open within 2 minutes. If the switch operates correctly, check for
proper installation of the switch.
5. Remove meter and jumper.
The SteamCraft V water level controls employ resistance sensing control
circuits The control circuit uses a high frequency (15 to 20 kHz) AC current
source with an open circuit voltage of 0.6 V RMS (+5%) between the shell
of the steam generator and the sensing probe. When water fills the tank
enough to contact the probe flag, current flows from toe generator/control
board ground through the water, the probe, and the wiring back to the
control board, completing the circuit. This current flow triggers the
appropriate switching action, i.e., turning off the water fin solenoid when
current flows in the water level probe circuit.
Current flow through any circuit is a function of both the voltage and the
resistance of the circuit. As water level rises to and over the lower edge of
the probe (or flag), resistance decreases. At some level, the resistance
decreases to the nominal set point. The associated current increase
triggers the switching action that, for example, closes the fill valve. The set
point resistance is expressed as a nominal DC resistance value and does
not include the reactive (AC) characteristics of the water in the.. cont.
Printed 4/90