I have a powerstar ae115 water heater that is 3 years old. The thermal cutout onthe left side keeps tripping. after shutting off the shower the temp on the top of the unit is reaching 185*f. I have cleaned out the heating element,inlet screan, and all faucet outlets.with no change. any advice would be greatly appriciated. Thanks Ralph V.

5 years is about the lifespan for tankless.
You might have shorted element. That would explain cooler water and tripping reset.
Test element: power is off, disconnect wires from element; ohms = voltage squared divided by watt rating of element
http://waterheatertimer.org/How-to-test-water-heater-element.html

Call service technician./ Call Bosch
http://waterheatertimer.org/pdf/Bosch-AE115-AE125_manual.pdf

Gene

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Water leaking into elements. Bad PC board. Undersized breakers. Undersized main panel.
Bosch Powerstar is a computer that happens to heat water.
If your 5-year-old laptop computer was malfunctioning, you would not be surprised.
But for some reason (false marketing by manufacturers?), folks believe a tankless computer is going to last 20 years.
Moreover folks also believe tankless will provide endless hot water while saving money.
The whole idea of tankless saving money is a load of sales-BS that defies physics and common sense.
There are no service manuals... except bosch website has troubleshoot section in product manual.
Call a bosch-qualified service tech.
Go to Lowes and buy ordinary tank heater, and fix your heater today for only $250.
Tank-type electric water heater can be easily repaired and maintained by homeowner to last forever... that is a fact
http://waterheatertimer.org/How-to-maintain-water-heater.html

http://waterheatertimer.org/How-to-wire-Tankless-electric-water-heater.html

Gene

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

The left canister probably has a grounded element in it, which will keep power going after the water is off. Either that or you have a bad triac on your control unit

Problem might be crossover from failed single-handle faucet cartridge:
http://waterheatertimer.org/Crossover.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Product manual shows electro-mechanical thermal cutout page 9 but offers no troubleshoot steps except to say that overheating is cause.
http://waterheatertimer.org/pdf/Bosch-AE115-AE125_manual.pdf

http://www.bosch-climate.us/files/201009211859150.EP-23_Removing_and_replacing_element_assembly.pdf

Test elements:
Remove both wires off element.
Set multimeter to read ohms.
Watt and volt rating appear on side of each element.
Ohm = Volts squared divided by wattage.
For example:
Assume 240Volt circuit (240 Volts squared = 57600)
Assume 9000 watt element > check side of element for rating.
So 57600 divided by 9000 watt element = 6.4 ohms
http://waterheatertimer.org/images/ohm-reading-for-emements.jpg

Have you de-limed this unit?
Is there a check valve causing closed system in the plumbing, that might also cause decreased water flow?
Are there reduced-flow faucets or clogged aerators?
What happens when suspect cut-out element is no longer connected? The unit should continue heating.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Question posted under Bosch tankless.
Question says 'tank'
Brand, model, and type heater unknown.
Elements mean electric.
'Thermal cutout pops when taking shower produces cold water' indicates tankless, since tank-type would maintain some hot water.
No error code might indicate tank-type.
Add a comment with type, brand and model number of heater for possible assistance.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

9:10 times the control board is bad. You are wise to suspect as much.

Call BOSCH 800-798-8161 tech support. If it is not too old even out of warranty they will help diagnose. You can get parts for free in warranty and buy parts at www.houseneeds.com out of warranty. If it gets hot fast and then stops, one of the "Thermal cutout switches" is cutting out. The water flow it probably blocked. (Just a guess) On many models they have a "Screen" and or a "Gromet" that you can clean out. If your water is really hard the whole unit may be clogged. I believe the "SAFE" thing to do is replace it but again I say CALL BOSCH TECH SUPPORT. I have also heard of people "Cleaning the whole units with vinigar, like cleaning a coffee maker. TURN OFF POWER! TURN OFF H20! REMOVE UNIT, then clean.

You must run two seperate 8-2 lines and each line must be on a different phase

The PowerStar AE115 unit replaces the PS19T model which has been discontinued. Now's the time to upgrade...