Garland MP-GD-10-S, MP-GS Testing & Troubleshooting, Mechanical Control, Fast Control

TESTING & TROUBLESHOOTING

MP-GS-10/20 Troubleshooting Guide

Use this chart with the appropriate wiring diagram, also found in this manual

Mechanical Control

PROBLEM	POSSIBLE CAUSE	CORRECTIVE ACTION
Fan will not Run	No Power to Oven	Turn power on
	No Power to Oven	Check Light circuit – IF OK, Select “Cook” and Check
		Timer circuit.. IF OK, Check Door Micro Switches
	Micro switch not OPENING	Check connections & switch functions..
		(Caution: the switch components on this control
		system pass 115 v.. a..c.. through switch contacts..)
	Fast Control
PROBLEM	POSSIBLE CAUSE	CORRECTIVE ACTION
Key Pad Buttons Not	Defective key pad	Use key pad diagnostics / pin outs test points
Responding
	Loose ribbon connection at key pad	Check connection
PROBE ERROR in display	Faulty Probe	Replace probe
	Loose probe connection	Check connections
HI TEMP In display	Oven at too high a temp for product	Allow oven to cool
HELP In display	Faulty Probe	Replace probe
	Motor centrifugal switch stuck	Check centrifugal switch
	Gas valve (s), or Ignition System	Check heat generation system – ( Refer to Service
		procedures (Heat generation system) -..page
Unit will not shut off	Unit above 150°F	Put unit into cool down, open door slightly
No HIGH speed But LOW	Bad key pad	Use diagnostic KEY PAD TEST
speed works
	Bad K2 relay on board	Check for voltage out of K2 relay
	Bad motor	Check motor
No LOW speed But HIGH	Bad key pad	Use diagnostic KEY PAD TEST
speed works
	Bad K2 relay on board	Check for voltage out of K3
	Bad motor	Check motor
Display is BLANK NO	Bad transformer	Check for 24VAC out of TR1 transformer
POWER
	Bad harness connection	Check connections
Unit will not heat	No power out of K4 relay	Check for power out of K4 relay
	No power out of Ignition Module MV	Complete a flame current check to osolate
	Gas valve shutoff switch open, PV, MV,	Check for MV power at gas shutoff switch, and that
	or both valves stuck closed	PV and MV opens on call for heat
	Motor centrifugal not closing	Check motor centrifugal switch
Motor stops, then after a	Thermal Trip on motor	Inspect rear clearance
period of time comes back
		Motor air intake is clear of lint/debris
on
		Replace motor

Page 46 Part # MPSM07 (03/24/08)