Troubleshoot GWH 635 ES Bosch ProTankless Gas Tankless Water Heater

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GWH 635 ES Tech Support

Troubleshoot

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GWH 635 ES Technical Support

THIS MODEL IS FOR INDOOR INSTALLATION ONLY.

Please note: If you are unable to perform the tasks listed below or need additional assistance, please contact your original installer/licensed gas technician.
Visit our Service Installer Locator to find an installer nearest you.

635ES Troubleshooting

Q. Burners Do Not Ignite When Hot Water Is Turned On?

Q. Water Is Too Hot?

Q. Water Is Not Hot Enough?

Q. Low Water / Flow Pressure?

Q. Hot Water Temperature Fluctuates At Tap?
Note: Temperature fluctuations from hot to cold during use are typically caused by a restriction in the hot water plumbing. This slows the flow within the tankless heater, decreasing it below the activation flow rate, which shuts off the burners. The end result is nothing but cold water coming out of the outlet. Follow each step below before proceeding to the next. After each step, test the hot water flow to see if it remains constant without turning cold.

Q. Noisy Burner / Heater During Operation?

Troubleshooting Error Codes

Please note: If there is a problem with the installation, venting or operation of the unit, the heater will communicate the source by these error codes.