Thomas & Betts RZ-NA 441-OMS Troubleshooting, Symptom or Problem, Cause and Remedy

19. Troubleshooting

Chart 1 - General Troubleshooting Guide (Check the diagnostic lights on the circuit board)

Symptom or Problem	Cause and Remedy
1. Disconnect switch is closed, but "control power" light is not lit.	1. Fuses are missing or blown in disconnect switch - replace fuses.

2.Transformer not wired according to diagram - check wiring.

3.Secondary 8A fuse (on transformer) is missing or blown - replace fuse.

4.Indicator light is burned out - replace bulb (P/N 125189).

2.Disconnect switch is closed, but "firestat normal" light is not lit. 1. See causes and remedies for Problem 1 above.

2.Optional control relay or door switch contacts are open - to test, jump terminals 3 to 4 or 1 to 2.

3.Firestat option not ordered - verify order/wiring diagram.

4.Firestat manual reset tripped - reset firestat control.

3. Disconnect closed, blower switch in test position,	1.	Freezestat option not ordered - verify order/wiring diagram.
"firestat" light is lit, but "freezestat" light is not lit	2.	Freezestat relay contacts are open - checking setting on control.
	3.	Indicator bulb is burned out - replace bulb (P/N 125189).
4. Disconnect closed, blower switch in test position, "firestat" and	1.	End switch on damper motor not closed. - check end switch wiring.
"freezestat" lights are lit, but "starter energized" light is not lit	2.	Faulty damper relay - replace relay.
and the blower motor is not operating.	3.	Damper motor miswired - rewire damper motor per wiring diagram.
5. Disconnect closed, blower switch in test position,	1.	Blower motor not wired correctly - check wiring diagram on motor.
"firestat", "freezestat" and "starter energized"	2.	Faulty motor starter - replace (check coil first).
lights are lit, but the blower motor is not operating.	3.	Faulty blower motor relay - replace relay.
6. Disconnect closed; blower switch in test position; "firestat",	1.	Low air switch open - verify pressure drop at burner.
"freezestat" and "starter energized" lights are lit and the	2.	Indicator light is burned out - replace bulb (P/N 125189).
blower motor is operating; but the "low air light" is not lit.	3.	Faulty low air switch - replace pressure switch (P/N 86986).
7. Disconnect closed; blower switch in test position;	1.	High air switch open - verify pressure drop at burner.
"firestat", "freezestat", "starter energized" and "low	2.	Indicator light is burned out - replace bulb (P/N 125189).
air" lights are lit and the blower motor is operating;	3.	High air switch option not ordered - verify order/wiring diagram.
but the "high air light" is not lit.	4.	Faulty high air switch - replace pressure switch (P/N 86987).
8. Disconnect closed; blower switch in test position; "firestat",	1.	Indicator light is burned out - replace bulb (P/N 125189).
"freezestat", "starter energized", "low air" and "high air"	2.	Tripped manual reset limit control(s) - reset manual control.
are lit; but the "limit control normal" light is not lit.	3.	Faulty manual limit control (s) - replace limit control.
9. Disconnect closed; blower switch in test position;	1.	Indicator light is burned out - replace bulb (P/N 125189).
"firestat", "freezestat", "starter energized", "low air",	2.	High ambient control option not ordered - verify order/wiring diagram.
"high air" and "limit control normal" lights are lit;	3.	High ambient control contacts open - check setting on control.
but the "ambient (outside air) cutoff normal" light is not lit.
10. Disconnect closed; blower switch in test position;	1.	Indicator light is burned out - replace bulb (P/N 125189).
"firestat", "freezestat", "starter energized", "low air",	2.	Low gas pressure switch option not ordered - verify order/wiring diagram.
"high air", "limit control normal" and "ambient (outside air)	3.	Low gas pressure switch contacts open - check setting on control.
cutoff normal" lights are lit; but the "low gas	4.	Low gas pressure switch contacts open - check gas pressure.
pressure normal" light is not lit.	5.	Faulty gas pressure switch - replace gas pressure switch.
11. Disconnect closed; blower switch in test position;	1.	Indicator light is burned out - replace bulb (P/N 125189).
"firestat", "freezestat", "starter energized", "low air",	2.	High gas pressure switch option not ordered - verify order/wiring diagram.
"high air", "limit controls normal", "ambient (outside air)	3.	High gas pressure switch contacts open - check setting on control.
cutoff normal" and "low gas pressure normal" lights are lit;	4.	High gas pressure switch contacts open - check gas pressure.
but the "high gas pressure normal" light is not lit.	5.	Manual reset on switch tripped - reset pressure switch manual reset.
	6.	Faulty gas pressure switch - replace gas pressure switch.
12. Disconnect closed; blower and burner switches in run	1.	Lack of power at L1 on ignition module - ECO blown, find
position; control switch is in "winter" position;		cause then replace ECO.
"control power", "high gas normal"; "low gas normal";	2.	Faulty burner enable relay - replace relay.
"firestat normal"; "system switch energized"; "starter	3.	Low stage relay contacts are not closed - check air controller or
energized" and "freezestat normal" lights are lit; but		thermostat setting.
ignitor is not becoming energized or beginning to glow.	4.	Faulty low stage relay - replace relay.
	5.	Faulty hot surface ignitor - check continuity at the ignition module
		and circuit board. If reading is greater than 5-6 ohms, replace ignitor.
	6.	Faulty ignition module - replace entire module.
13. Disconnect closed; blower and burner switches in run	1.	Ignitor not reaching 1.4A threshold - check voltage and
position; control switch is in "winter" position; "control power",		current to ignitor.
high gas normal; "low gas normal"; "firestat normal"; "system	2.	Faulty hot surface ignitor - check continuity, replace ignitor.
switch energized"; "starter energized" and "freezestat normal"	3.	Faulty ignition module - replace entire module.
lights are lit; ignitor glowing but "pilot valve normal" light
(thus the pilot valve) is not energized.
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