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Table 17. Thermal Fuse / Overheat Switch.
Wire Color Voltage Resistance
Connector
No.
Pin
Nos.
Red-Red 11-13 VDC Below 1 ohms
F6
H1
F6-
H12
Flame Rod:
Place one lead of your meter to the flame rod and the other to ground. With the unit running, you should
read between 5-150 VAC. Set your meter to µ amp scale and series your meter in line with the flame rod.
You should read 1 µ amp or greater for proper flame circuit. In the event of low flame circuit, remove the
flame rod and check for carbon or damage.
Heat Exchanger and Outgoing Water Temperature Thermistors:
Check all Thermistors by inserting meter leads into each end of the thermistor plug. Set your meter to the
20k scale and read resistance. Applying heat to the thermistor bulb should decrease the resistance.
Applying ice to the thermistor bulb should increase the resistance. See below for examples of typical
temperatures and resistance readings.
Example: 59ºF = 11.4-14kΩ 140ºF = 2.2-2.7kΩ
86ºF = 6.4-7.8kΩ 221ºF = 0.6-0.8kΩ
113º = 3.6-4.5kΩ
Table 18. Outgoing Water Thermistor.
Wire Color Voltage Resistance
Connector
No.
Pin
Nos.
White-White n/a
See example
above
F5 3-4
Table 19. Heat Exchanger Temperature Thermistor.
Wire Color Voltage Resistance
Connector
No.
Pin
Nos.
Pink-White n/a
See example
above
F4 3-11
Table 20. Intake Air Thermistor (Indoor Model Only).
Wire Color Voltage Resistance
Connector
No.
Pin
Nos.
Orange-White n/a
See example
above
F3 3-12
Table 21. Surge Protector.
Wire Color Voltage Resistance
Connector
No.
Pin
Nos.
Black-White 108-132 VAC n/a D2 1-3
Blue-Brown 108-132 VAC n/a D1 1-3
With the power off, you can check the continuity through the surge protector. Place a meter lead on the
top pin #1 of the surge protector and pin #3 on the bottom of the surge protector. Check across the top
pin #3 and the bottom pin #1. If you read continuity across these two points, the surge protector is good.
If you do not get continuity, replace the surge protector.
Table 22. Remote Controls.
Wire Color Voltage Resistance
Connector
No.
Pin
Nos.
Terminals B1 10-13 VDC 1.5-3.0k ohms B 1-3