Bosch Water Heaters - Recent Questions, Troubleshooting & Support


id say if the plumber charged you to call him back right away

Bosch Water... | Answered on May 06, 2019


ABSOLUTELY NOTHING YET AS IT HAS NOT FAILED . WHY MAKE A MONEY PIT OF IT BEFORE ANY THING GOES WRONG ?A GOOD PRE-FILTER MIGHT HELP AS MUCH AS ANY THING ELSE

Bosch Water... | Answered on Mar 26, 2019


It could be the thermostat sensor They usually have a carbon buildup. They are easy to install and not that expensive. Good luck

Bosch Water... | Answered on Mar 26, 2019


That particular tankless water heater has hydro-generated ignition. In order for it to function, it requires a certain water pressure and velocity. You can try turning on the hot water in two location in your house to see if that gets it started. If it does, try getting a higher flow shower head, or removing the limiters in your faucets.

Bosch AquaStar... | Answered on Jan 31, 2019


as with all water heaters they need flushed once in awhile to get rid of sediment in the bottom of the tank . knowing this from the get go most of us never seem to get around to doing it . even myself but I do have a unit that is supposed to prevent this by the dip tube that was built in has circular action in the bottom of the tank

Bosch Water... | Answered on Jan 20, 2019


If there is not a clicking sound, it almost always means the main ignition or control unit (box with red and green lights and wires coming from it) is not getting the supply voltage. The voltage is supplied by a generator that is getting energy from the flow of water (the "hydro generator"). First disconnect the wire connector at the hydogenerator and check the voltage while water is running. The manual says you should read 1.6 VAC (I read 2.5 VAC). Make sure your voltage reader is on AC, not DC. If you have at least something like 1 VAC, then the next thing to check is the "microswitch" that allows the hydro generator voltage to reach the ignition unit. To check it, disconnect the other wire connector that is on the black wire coming from the hydrogenerator that is closer to the ignition unit. Then with the water running, stick a small screwdriver in the male plug side to short the two wires in order to bypass the microswitch (per Bosch tech support instructions). You should now here clicking and see the unit work. This is what happened with me and tech support said I needed to order a new microswitch and gave me a part number and telephone. But don't stop reading here. You can see the microswitch when looking up at the underneath of the unit. It's a small white 1x1 inch box-like shape held by 1 screw. After removing it, I noticed the microswitch had a removable cover (which is strange for a switch) and opened it to discover the internal switch can actually move inside because it "automatically adjusts" itself when it is first put in (it stays more firmly, but not rigidly in place when the cover is on). So you can mess up when putting it in. Don't bump it. It can easily get out of its working range of motion, which is why mine stopped working: it was a bad design to use this type switch in this application. So I slide the internal switch back close to the spring side ("default" position), put the cover back on, carefulyl screwed it in place, and now it works.

The purpose of the mechanical microswitch is to not allow the hydroenerator voltage to the ignition unit unless the "pushrod" has opened the main gas supply. It prevents clicking if there is no supply gas, so it is not needed (you can electrically bypass it with a splice) if everything else is working fine. But don't blame me if you do this and for some reason it ruins the more expensive ignition unit. The microswitch is turned on by the pushrod when the pushrod leaves it's default position. The the pushrod moves only about 2 to 3 mm when you turn on the water. You can see the pushrod when you unscrew the microswitch, and you can watch it move. The problem is that the microswitch mounting is not precise enough for the small pushrod movement and the pushrod's default position can change with age of the diaphragm or change in the grease. So their automatically adjusting microswitch that makes up for lack of precision in design and pushrod movement can stop working when the pushrod changes position. My unit was 2 years old.

Bosch 1600H-NG... | Answered on Dec 18, 2018


It would be on the thermostats.

Bosch Ariston... | Answered on Oct 26, 2018

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