Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 3
BTC 770502101 A | 01.2019
Data subject to change
Table of Contents
1 Key to Symbols and Safety Instructions 4
1.1 Key to Symbols 4
1.2 Safety 4
2 Troubleshooting 6
2.1 Electrostatic Discharge (ESD) Precautions 6
2.2 Resetting From Lockout 6
3 Error Flash Codes 7
3.1 No Flash and No Fan (System Does Not Start Normally) 7
3.2 7 Flashes (System Lock-Out due to Failed Ignition)
8 Flashes (System Lock-Out due to too Many Flame Dropouts) 10
3.3 2 Flashes (Low Fire Pressure Switch Stuck Closed) 12
3.4 3 Flashes (Low Pressure Switch Stuck Open)
6 Flashes (Pressure Switch Cycle Lockout)
13 Flashes (High Pressure Switch Stuck Open) 14
3.5 4 Flashes (Limit/Rollout Switch Open Less than 5 Mins)
5 Flashes (Limit/Rollout Switch Open More than 15 Mins)
11 Flashes (Limit/Rollout Switch Open from 5 to 15 Mins) 16
3.6 9 Flashes (Incorrect Polarity of L1/L2) 20
3.7 Rapid Flashes (Low Flame) 21
Appendix A - Sequence of Operation 22
Two Stage Controller Logic 22
A1 Heating Modes 23
A1.1 Low Fire Heating Mode Logic (only W1 signal): 23
A1.2 High Fire Heating Mode Logic (W1+W2 Signal): 24
A2 Ignition Failure and Reignition Sequence 25
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