I HAVE A POWERSTAR AE115 AND THE WATER IS WARM AND NOT AS HOT AS IT WAS CHECKED THE THERMAL CUT-OUTS AND THEY ARE IN A DOWN POSITION AND DO NOT SPRING UP AND DOWN SO I DONT THINK THEY ARE TRIPPED AND HAVE NOT ADJUSTED THE TEMPERATURE AND REDUCED THE FLOW BY CLOSING THE INLET VALVE A LITTLE WHAT COULD IT BE?

SOURCE: Bosch PowerStar125 won't heat and I can't get one element to work

It sounds like you have a copper canister unit. Ohm out the elements in that one canister. the directions are on the websight for bosch, or I can walk you through it. But you will need a digital multimeter to do this. If you have a blown element in that one canister, then the tco will not reset.

SOURCE: I have a powerstar ae115

You've done the required first-step troubleshooting and maintenance.
If thermal cutout keeps tripping, and unit is actually reaching 185, then something is wrong with wiring, temperature sensor, gas valve, or PC board. Or combination of factors.
Call service technician, and open following link for some Bosch tankless resources including Bosch contact information:
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

SOURCE: Bosch AE115 with new pc

Hi,
It seems as though the thermal cutout is also bad and is tripping out at too low of a temperature...

I would replace the thermal cutout also, as it seems to also be bad...

Running the extra water keeps the temperature just low enough to keep the cutout from tripping out...

heatman101

SOURCE: PowerStar AE125 seems to have failed

the circuit board is gone bad, try this, with power off reset the overload on the heater.Turn power back on and turn on water to the unit. with no taps open hold the pipe near the left element for a few minutes. it will most likely getting verry hot and trip the overload.(this is done with no water running and power on to the unit).you may even hear the water in the left elemnet start to boil or sizle. the reason for this is the triacs on the cir board are bad.I have troubleshoot this troblem many times. the design is bad and their in now a new unit (redesign) out . bosch knows their junk and wont cover them beyond 1 yr. one way around it is call tech at bosch and tell them its leaking. the u will get one of the new designs. Also applies to the AE125, Rp27pt