Question about Bosch & Tankless LP Hot Water Heater

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Bosch 240fx, power surge destroyed mother board. Replaced MB and now fires, shuts down, fires, shuts down, fires and shuts down and top light flashes. Cleaned the flame sensor still doing the same thing. Cleaned flow sensor, works as it should. What the heck is wrong with this thing?

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Check fan sensor

Posted on Aug 03, 2010


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SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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I'm assuming this is a 240FX. Sounds like a control board issue. Since this was such a rare machine, the board cost 3/4 the cost of a new unit, and was not something recommended to replace.

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It sounds like a bad flo switch. If not, then the problem is more likely in the mother board. Call Bosch back and ask for a supervisor right away. The peons sometimes are given advancement according to how many calls they handle, so they have a time crunch. Go right to the supervisor. Good luck!

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These are very finicky units. However, it comes down to power from the breaker, internal fuse, and sensors. If the fan was damaged by a power surge or from being improperly grounded, you can be chasing your problem for a while. I highly recommend replacing it with a Bosch as they are fully serviceable and the new units have a very clear error code file. It brings you right to the source. Check for a service provider to install it for you.

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Electronic fire. fires up , Shuts down after 5 sec.

it sounds more like you have the ignitor wire shorting out on metal and won't allow it to stop trying to light the burner, hold the wire away from any metal and see if it helps, if this isn't the caee your circuit board needs to be replaced,

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Here is the run down>
Water too cold Neon light on:
1). Water flow is too high-adjusting the water flow as follow; open fully both inlet and outlet shut-off valves at the heater, then turn on fully the highest flowing hot water faucet closest to the outlet connection. Adjust the outlet shut-off valve until the water flow from the hot faucet corresponds to the approximately 3.6gal/min at 105 degree.
2). One of the power supplies is not on-check the breaker box, there should be three ganged breaker, each corresponds to each of the heater power supply.
3). The power supply voltage has dropped-reset the breaker in the breaker box.
4). Temperature dial is turned too low- temperature adjustment is made using the dial on the bottom edge of the unit. The adjustment is between approximately 95 and 135 degree F. Turning the dial clockwise increase the temperature settings.
5). The inlet water temperature has dropped-readjust the temperature dial.

Attached link is for Bosch hotwater heater installation. This should give you idea as to what to look for.
The following link is Basch Hotwater troubleshooting Q&A, this should also give you some help.

Please post back on this thread, If you still having problem.

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