Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 3 Table of Contents 1 Key to Symbols and Safety Instructions 1.1 Key to Symbols 1.2 Safety 2 Troubleshooting 2.1 Electrostatic Discharge (ESD) Precautions 2.2 Resetting From Lockout 3 Error Flash Codes 3.1 No Flash and No Fan (System Does Not Start Normally)
4 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide 1 Key to Symbols and Safety Instructions 1.2 Safety Please read all instruction in the manual and retain all manuals for future 1.1 Key to Symbols reference. Warnings WARNING: Untrained personnel (homeowners) may only clean and replace filters and replace fuses as required ...
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Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 5 WARNING: FOLLOW ALL SAFETY CODES WARNING: FIRE, EXPLOSION Wear safety glasses, protective clothing, and work Check entire gas assembly for leaks after lighting this gloves. Have a fire extinguisher available. Read these appliance.
6 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide 2 Troubleshooting 2.2 Resetting From Lockout Furnace lockout results when a furnace is unable to achieve ignition after three attempts. Refer to the troubleshooting chart on the following pages for assistance in determining the source of unit operational problems.
Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 7 3 Error Flash Codes 3.1 No Flash and No Fan (System Does Not Start Normally) Troubleshooting Chart Start Correct Are there any wiring loose wires or wrong according to connections? wiring diagram...
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8 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide No Flash and No Fan (System Does Not Start Normally) Figures & Tables 1. Check for 18-31Vac power between these 2 terminals with multi-meter. Figure 3 1. Check for 115Vac power supply between L1 and common terminal Figure 1 1.
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Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 9 1. Check for 18-31Vac power between “W/W1” & “C” terminals with multi-meter Figure 5 1. Check for 18-31Vac power between Hi-heat/lo-heat/hi-cool/lo-cool and COM with multi-meter 2. Check for 115Vac power supply between CIRC-H and N with...
1 0 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide 3.2 7 Flashes (System Lock-Out due to Failed Ignition) 8 Flashes (System Lock-Out due to too Many Flame Dropouts) Troubleshooting Chart Start Correct wiring Are there any according to loose wires or wrong...
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Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 11 7 Flashes (System Lock-Out due to Failed Ignition) 8 Flashes (System Lock-Out due to too Many Flame Dropouts) Figures & Tables 1. Check for 9-17Ω between these two terminals with multi-meter.
1 2 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide 3.3 2 Flashes (Low Fire Pressure Switch Stuck Closed) Troubleshooting Chart Start Correct wiring Are there any according to loose wires or wrong the wiring connections? diagram Does the resistance of low fire...
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Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 13 2 Flashes (Low Fire Pressure Switch Stuck Closed) Figures High fire pressure switch Low fire pressure switch Overflow pressure switch Figure 12 1. Check for ∞ resistance between these two terminals with multi-meter.
Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 15 3 Flashes (Low Pressure Switch Stuck Open) 6 Flashes (Pressure Switch Cycle Lockout) 13 Flashes (High Pressure Switch Stuck Open) Figures T he pressure switch that you are checking in this step depends on the number of LED fl...
1 6 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide 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) Troubleshooting Chart Start “SW2”...
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Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 17 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) Figures & Tables 1.
2 0 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide 3.6 9 Flashes (Incorrect Polarity of L1/L2) Troubleshooting Chart Start Correct the wire connection(black and white wire) according to wiring diagram. See Figure 23. Figures BLOWER DOOR SWITCH 115V FIELD-...
Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 21 3.7 Rapid Flashes (Low Flame) Troubleshooting Chart Start Replace the gas Adjust the gas valve valve if the to ensure manifold pressure cannot gas pressure meets be adjusted the required values...
2 2 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide Appendix A - Sequence of Operation Two Stage Controller Logic A1. There are two heating modes: A1.1 Low Fire Heating Mode: Only W1 signal A1.2 High Fire Heating Mode: Both W1 and W2 signal ...
Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 23 Heating Modes A1.1 Low Fire Heating Mode Logic (only W1 signal): Figure 24 When there is a call for heat (W1), the inducer will start on HIGH speed and the low pressure switch closes. This will last for 15s.
2 4 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide A1.2 High Fire Heating Mode Logic (W1+W2 Signal): Figure 25 When there is a call for heat (W1), the inducer will start on HIGH The blower motor will run at high speed for 30s for fan delay.
Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 25 Ignition Failure and Reignition Sequence If the furnace fails to ignite, there is a separate logic for the re-ignition sequence: Figure 26 When there is a call for heat (W1), the inducer will start on HIGH speed and the low pressure switch closes.
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2 6 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide Data subject to change 01.2019 | BTC 770502101 A...
Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 27 BTC 770502101 A | 01.2019 Data subject to change...
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United States Bosch Thermotechnology Corp. 65 Grove Street Watertown, MA 02472 Tel: 866-642-3198 Fax: 603-965-7581 www.boschheatingandcooling.com BTC 770502101 A | 01.2019...