C4 76 error code c4 - 76 flashes c4 then 76 tries to run then shuts down

Sounds like the heating element is gone. Look up the code on the manufacturer's web site under customer support.

hi pruzek.
try this link might help you out.
LG dishwasher flashing AE error code Google Search

Troubleshoot and error codes following link:
http://waterheatertimer.org/pdf/RTG-error-codes-3.pdf

Not getting gas, low gas pressure, air in gas line, igniter not aligned with burner, wires disconnected, unit not grounded ...

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

The year 2009 Bosch 24ES manual does not show error code 14.
Your manual may be different.
Call Bosch 1-800-642-3111
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html
http://waterheatertimer.org/pdf/Bosch-GWH2400ES.pdf

Don't forget to read the product manual for required yearly maintenance, and performing this maintenance will eliminate many common error codes.

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

I recently had a similar problem with my N-132M-ASME heater. The unit would come on, then shut down and flash Error Code 21. According to the owners manual, that code indicates the unit is not getting enough air. I tried vacuuming the unit, blowing it our with air and checking to be sure the exhaust lines were clear. Nothing helped. A service technician came out and recommended I descale the unit and clean the burner. I did this but the problem did not go away. He also suggested I replace the Burner Sensor. It's not an expensive part, around $20. I ordered the part and have not had a problem since I installed it. Hope this helps.

Before calling service technician, open following link for Rheen troubleshooting resources and possible error code help plus link to Rheem chat:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Typically, error codes are start-point for troubleshooting.
Error 76 is communication fault with remote control, which can be bad remote, bad wire, bad wiring connection, or bad part inside tankless.
C4 is oxygen sensor problem or bad venting.
More than 1 error code, or mixed error codes can indicate problem such as bad PC board -or- PCB.

I have a code showing C7 13 the heater runs for about 2 to 3 mins then shuts off. Any suggestions?

I do not have a solution for you, however mine does th same thing. Did you ever find a solution?

code 14 is a big deal shut that thing down! you will burn it up if you keep running it, your over heat wrap on the heat exchanger is too hot. call rheem they can walk you through it

chances of a critter in the fan? Like a dead 4 legged critter?