MHC-22 Holding Cabinet Items 86002 & 86003 Service, Installation And Operation Manual
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For customer service, call (989) 773-7981, (800) 733-8829, Fax (989) 773-3210, www.mercoproducts.com
Troubleshooting
Symptom
Possible Cause
Evaluation
Holding Cabinet will not heat
Incoming Power Supply
Verify power cord is secured firmly in receptacle. Measure
the incoming voltage. Check circuit breakers. Reset if
required. Call power company if needed.
Power Switch
Check continuity between switch terminals. Replace switch
as needed.
Unit doesn’t reach desired
temperature
Thermocouple
Check for continuity in circuit.
Heat Element
Compare cavity temperature with display reading. Insert
temperature probe into center of cavity. Acceptable
temperature variation is +/- 20° from display reading.
Check for loose connection.
Check the Amp draw on each element for proper load.
Check page 5 for rating information. If the amp draw is
high or low, check the individual elements for opens,
shorts and proper resistance.
WITH POWER OFF: To check resistance of the elements,
remove all leads from the elements and use a digital
multimeter.
The element resistance should be 120V – 87 ohms.
Replace heating element (shelf) as needed.
Check thermostat (common wire). Please note that if ther-
mostat is bad, both circuits will be bad.
Temperature is too high
Thermocouple
Check for incorrectly wired thermocouple. Thermocouple
wire polarities are reversed.
Heat Element
Compare cavity temperature with display reading. Insert
temperature probe into center of cavity. Acceptable tem-
perature variation is +/- 20° from display reading.
Check for loose connection.
Check the Amp draw on each element for proper load.
Check page 5 for rating information. If the amp draw is
high or low, check the individual elements for opens,
shorts and proper resistance.
WITH POWER OFF: To check resistance of the elements,
remove all leads from the elements and use a digital
multimeter.
The element resistance should be 120V – 87 ohms.
Replace heating element (shelf) as needed.
Display reads unusual
characters
Make sure wires are connected properly (grounded).
If wires are grounded properly, new control board is
needed.
On/Off switch doesn’t light
(but unit works properly)
Power Switch
Check wiring to switch.
