Desa DNV25NB, DNV40NB installation manual Troubleshooting, Observed Problem Possible Cause Remedy

OWNER’S MANUAL

TROUBLESHOOTING

Note: For additional help, visit DESA International’s technical service web site at www.desatech.com.

Note: All troubleshooting items are listed in order of operation.

WARNING: Turn off and unplug furnace and let cool before servic- ing. Unless you need gas supply for testing, shut off equipment shutoff valve before servicing. Only a qualified service person should service and repair furnace.

OBSERVED PROBLEM	POSSIBLE CAUSE		REMEDY
No heat	1.	Thermostat off	1. Check to be sure thermostat is calling for heat.
				Wire to thermostat could be off terminal
	2.	Gas supply	2. Be sure equipment gas valve is in the open posi-
				tion (level or parallel to gas line)
	3. Electrical connections and power		3. Be sure all electrical connections are secure
	4.	Motor	4.	Motor must be operating at top speed before
				burner will come on. If blower is not operating
				at top speed, check voltage supply (minimum
				100 volts A.C.). If voltage supply is okay, check
				for defective motor
	5.	Malfunctioning microswitch	5. Be sure the microswitch is sailing in far enough
				to open the solenoid valve and to energize the
				ignition control. If the switch is not sailing in,
				clean any dust or dirt from the actuator pin. Other
				reasons for the switch not sailing in are
				A. Insufficient blower speed - Slow motor due to
				faulty motor or lint and dust accumulation on
				the blower wheels or restriction of return air to
				the furnace
				B. Faulty microswitch - Replace switch if cir-
				cuit to ignition control is not completed when
				switch is manually engaged. Switch should
				also be replaced if blower motor running at
				top speed fails to engage switch within six or
				seven seconds. Note: To service switch, com-
				bustion chamber must be pulled out. Follow
				steps 1, 2, 3, 9 and 10 on page 8 to remove
				combustion chamber
	6.	Gas valve	6.	Within 20 seconds after motor reaches 75% of
				its r.p.m. and microswitch engages, check the
				following:
				A. Voltage at valve - If current is present but

valve is not opening, check wire connections B. If wire connections okay - Replace valve C. No voltage at valve - Check circuit completion

through microswitch and limit switch as well as wiring and wire connections. If no defects are found, see Ignition Failures, page 16

www.desatech.com Continued

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