Greenheck Fan VSU Heater Does Not Operate, Troubleshooting, Turn Heat Switch S4 On, Replace Fuses

Troubleshooting

Heater Does Not Operate

Does not attempt to light (No visible spark)

24 VAC between		No
terminals W1 and X?
	Yes
115 VAC between		No
terminals 102 and 101?
	Yes
115 VAC between		No
terminals 103 and 101?
	Yes

115 VAC between		No
terminals 104 and 101?
	Yes
Continuity between		No
terminals 107 and 108?
	Yes

Heat Switch (S4) Off

(Turn Heat Switch (S4) On)

Heat Switch Not Wired

(Wire Heat Switch (S4))

Primary Fuses Blown

(Replace Fuses)

Main Transformer (TR4) Defective

(Replace Transformer)

Inlet Air Sensor (TS) Holding

(Adjust TS setting — Reference Blower Start-Up Step #6)

Heat Relay (RH) Defective

(Replace Heat Relay (RH))

The power light on the flame safeguard should

blink approximately every 5 seconds as it

performs a self-diagnostics check.

High Limit (HLC) Tripped

(Reset/Replace High Limit (HLC)) (Check on cause of control loss)

Airflow Switch (PS) Holding for Proper Airflow

(Correct airflow across burner)

(Reference Direct Gas Start-Up Step #3)

At this time the heater should attempt to light.

(The pilot light on the flame safeguard should illuminate).

Model VSU Make-Up Air 15

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