MT3255 and MT3270
5 --- 3
CONVECTION SYSTEM
POSSIBLE CAUSE(S) SUGGESTED REMEDY
Symptom #1 --- Blower motor(s) not running
D
Blower switch off.
D
No power to the oven.
D
Motorfuseblown.
D
Faulty start capacitor.
D
Motor burned out.
D
Thermal overload tripped.
D
Novoltageatthemotorcontactorcoil.
D
Faulty motor contactor.
D
Turn switch to on position.
D
Verify power to t he oven. If there is no power de-
termine cause.
D
Replacefuse.Determinetheampdraw.
D
Replace capacitor.
D
Check draw (3 a mps or greater).
D
Determine if the cooling blower (or fans) are oper-
ating. If not, verify voltage to the cooling blower.
If voltage is present, replace the cooling blower
motor. If voltage is not present, verify voltage
through the thermal switch. If no voltage is pres-
ent, replace the thermal switch.
D
Check for blown fuse or bad blower switch.
D
Replace motor contactor.
Symptom #2 --- Blower motor(s ) d o not shut off
D
Faulty motor contactor.
D
Faulty thermocouple on Hi/Lo board.
D
Faulty Hi/Lo board.
D
Hi/Lo board is not a dj usted properly.
D
Replace contactor.
D
Refer to the chart on page 6---5 of the Technical
Appendix. If the readings do not match replace
the thermocouple.
D
Determine if 115 VAC is coming out of #7 with the
adjustable potentiometer turned completely
counter-clockwise. If voltage is still present, re-
place the board.
D
Check and readjust Hi/Lo board. Refer to page
4---6 of Calibration and Adjustment.
Symptom #3 --- Blower motor running backward
D
Motor off by thermal overload (other fans forcing
blower to spin).
D
Faulty capacitor.
D
Determine if the cooling blower (or fans) are oper-
ating. If not, verify voltage to the cooling blower.
If voltage is present, replace the cooling blower
motor. If voltage is not present, verify voltage
through the thermal switch. If no voltage is pres-
ent, replace the thermal switch.
D
Replace capacitor.
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