Question about Bosch 2700ES Natural Gas AquaStar AquaStar 2700ES Tankless Water Heat

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Bosch AquaStar 2700ES NG - C7 error

I installed the unit myself and on power on got a C7 error msg.
According to the manual, the primary fan is not rotating.
I checked the power supply and grounding as well as visually inspected the unit inside to make sure there are no loose cable connections.
Any help is appreciated.

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  • gtodorov Feb 01, 2009

    Fixed the problem myself.

    The cables in the control panel attach to the PCB board with connectors that are little flaky.

    The pins in the connector on the multi-wire cable feeding the primary fan were bent outwards and were not making contact with the copper fingers on the PCB board. All it took to fix the problem was a screwdriver and a pin to adjust (bent inwards) the connector pins.

    Overall, a great unit after two days of use but I didn’t expect to have to take it apart to make it work. It’s German engineered after all.



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Hope this helps. Be careful of electrical shock!
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Posted on Jan 30, 2009


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C7 error code

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First, look for 120V to either the left or right pair of wires in the molex plug on the fan. if you have voltage, then the fan is bad. If you dont, its either just a fuse, the board is bad, or the fan is bad causing the fuse to blow. Insert the supplied spare fuse, and power up the unit. If it blows the fuse again, its the fan.

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