3 Troubleshooting (continued)
Checking temperature sensors
The appliance temperature sensors (inlet water, outlet water, system water, tank water, flue, and outdoor air) are all resistance type devices. The following tables show the correct values for the sensors at various temperatures. Use an ohmmeter to read the resistance of the sensor at a known temperature. If the resistance of the sensor does not closely match its corresponding table, replace the sensor.
Table 3B Inlet/Outlet/System/Tank Sensor Resistance vs. Temperature
S1a Inlet/Outlet/System/Tank |
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| (Wire Color - Bk and G) |
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Temperature | Resistance | Temperature | Resistance |
| Temperature | Resistance | Temperature | Resistance |
50 | 19,553 | 158 | 2,004 |
| 50 | 40,030 | 158 | 3,478 |
68 | 12,690 | 176 | 1,464 |
| 68 | 25,030 | 176 | 2,492 |
86 | 8,406 | 194 | 1,084 |
| 86 | 16,090 | 194 | 1,816 |
104 | 5,715 | 212 | 816 |
| 104 | 10,610 | 212 | 1,344 |
122 | 3,958 |
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| 122 | 7,166 |
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140 | 2,786 |
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| 140 | 4,943 |
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Table 3C Outdoor Air Sensor Resistance vs. Temperature
Temperature | Resistance | Temperature | Resistance |
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490,813 | 20 | 46,218 | |
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336,606 | 30 | 34,558 | |
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234,196 | 40 | 26,099 | |
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165,180 | 50 | 19,900 | |
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118,018 | 60 | 15,311 | |
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0 | 85,362 | 70 | 11,883 |
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10 | 62,465 | 80 | 9,299 |
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