My ae 125 electric tankless w/h the light flashes when turning on water I have to slow it down real slow

Hey Andy. Do you have your owners manual? There should be a section near the back that will break down the diagnostic code the flashing light is giving you. If not remove the front cover and look inside should be a wiring diagram and light legend.

Turn circuit breakers fully off and then back on.
Use nose to smell for burning inside main panel.
Make sure you are getting 240Volt and not just 120V from one leg of the breaker.
Do stress test on breaker panel.
http://waterheatertimer.org/Troubleshoot-household-electricity.html#stress

Least expensive solution: Replace tankless computer for $285 buying tank-type electric water heater from local box store.

If tankless computer is new, then call installer.
If you installed it yourself, call professional installer.
http://waterheatertimer.org/How-to-wire-Tankless-electric-water-heater.html

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

Copy following link:
http://waterheatertimer.org/How-to-wire-Tankless-electric-water-heater.html
AE115 has two elements and requires two 40 amp breakers.
A#125 has three elements and requires three 40 amp breakers, and is considered 'whole-house'
Do not install a tankless water heater because they cost more to install, and cost more to operate and maintain..
Add a comment and ask question.

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

This is a "point of service" tankless water heater that was manufactured by BOSCH. BOSCH is now Bosch-Climate.us. Technical support is available at 866-330-2729. P.S. check this site: http://tanklesswaterheaterz.com/bosch-ae-9-5-powerstar-1-5-gpm-point-of-use-indoor-tankless-electric-water-heater-reviews/

1) Cheapest and most reliable solution: Install tank-type electric water heater from local box store for $250. Get store coupons, offer 10% off store price. Repairs are made same day with generic off-the-shelf parts.
http://waterheatertimer.org/pdf/How-to-install-electric-water-heater.pdf

2) Install grundfo water pressure boosting pump.
http://www.ronhazelton.com/projects/how_to_increase_water_pressure_in_your_home
http://waterheatertimer.org/How-to-solder-pipes.html

3) Remove areators and low flow shower heads, Maintain unit as shown in product manual: Delime tankless unit yearly, Clean water filter monthly.

4) Call city and report low pressure and report issue as fire hazard, move to different apartment. Call apartment complex and ask why they didn't read flow requirements for tankless before installing tankless.

5) Call Bosch 866-330-2729 and complain that nobody read the flow requirement or tested local water flow before installing tankless.

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

All resets and breakers trip with high heat.
Do you mean the tankless unit is tripping the 40 amp circuit breaker?
Or the thermal cut-out, located on unit, is tripping?

Is this a new installation?
Or was the tankless working before and stop working?

Copy following link to check wiring.
AE 9.5 requires 40 amp breaker and 6 gauge wire.
http://waterheatertimer.org/How-to-wire-Tankless-electric-water-heater.html

If the unit is tripping the thermal cut, -out, then product manual says to call Bosch or service technician.
Call Bosch 866-330-2729
http://waterheatertimer.org/pdf/Bosch-Powerstar-AE3.4-7.2-9.5.pdf
Thermal cut-out can trip if water flow is too low.
Try changing power selector screw from Hi to Lo so only 1 element is ON. See diagram page 6 of manual.
Adjust the 'outlet service valve:' The manual recommends that a ball valve be installed between hot outlet and faucet. Adjust the valve so more water flows to faucet.
Remove aerator, clean aerator, don't use low flow restrictions or low flow shower heads, replace leaky faucet cartridge on single-handle faucet.

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

Before calling service technician, open following links for Bosch error codes, and contact information, and possible product manual for your model, etc:
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html
http://waterheatertimer.org/pdf/Bosch_EA_error_code_troubleshooting.pdf
http://waterheatertimer.org/pdf/Bosch-GWH2400ES-error-codes.pdf
http://waterheatertimer.org/pdf/Bosch_A4-E4_error_code_troubleshooting.pdf

Error code AE is not shown, but error EA means "burner flame not recognized by control unit when water is flowing"

There is also error A3 and A3 E3: jumper connection is not correct

Any suggestion could include a list of possible problems from bad PC board, burned out element, bad sensor, loose wire, or combination or these.
More information is needed to make a guess.
Test elements for continuity.
Check wires for loose and burned connections.
Open TP valve and test if hot water is available at machine.
If water at TP valve is hot, then problem might be plumbing-related, for example crossover.
http://waterheatertimer.org/Crossover.html

good luck,, there aren't that many whole house electric tankless units of any kind even made