Switching the water pump on,the red light comes on then there is a click in the heater what can cause it.

Check the pump is no seized

Could be your igniter or possibly your control board. The red light not being on indicates you most likely have an electrical issue. Check your breaker as well. If you nee any parts this site will have them all

http://www.suburbanrvparts.com/

Before calling service technician:
Click following link, the click product, then scroll to page bottom to tab that offers technical literature, and download service manual and operation manual.
http://www.hotwater.com/water-heaters/residential/hybrid/

Read the required installation and maintenance protocol to see if air filter has been cleaned regularly, or the condenser coil might be dirty.
Required maintenance can be done by service tech recommended by AO Smith.
Contact AO Smith to find trained person, and next time, do not install expensive water heater since all savings disappear with service issues.

Gene
h

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

Check the gas line orifice for a spider web. Its possible the gas is not able to get past the web.

You might have crossover problem caused by bad faucet cartridge.
http://waterheatertimer.org/Crossover.html

The green standby light should come on when 240Volt power is applied. Page 6 manual.
Both red lights should come on when tankless is activated. Page 6 manual

RTE 13 requires 60 amp breaker and 6 gauge wire
http://waterheatertimer.org/How-to-wire-Tankless-electric-water-heater.html
http://waterheatertimer.org/pdf/Rheem-TanklessElectricUC_AP15447.pdf

Factory temperature setting is usually default 120 degrees.
Adjust temps page 11 manual
Thermostat calibration is always approximate.
120 degrees is not hot enough to burn the skin.
Exceptionally cold incoming water temperature can cause tankless not to heat enough hot water: install tempering tank to preheat water to room temperature.
Tankless cannot be exposed to more than 11 grains hardness in water. Delime tankless yearly, clean water filter monthly, do not install low-flow restrictions or conserve water since the flow rate must remain high for tankless to activate.
Rheem does not post service manuals for their tankless water heaters.
Call Rheem 800 432-8373

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

the most likely cause is the heating element is bad. check the elements.

Most electronic ignition models only show the red light if there is a problem, (did not ignite) for one reason or another. To start with, make sure your propane is on, and you have a good flame at stove top burner, just to be sure the water heater is getting propane, and all air is bled from the line, which may cause water heater to go into check. (red light) If it does, shut switch off, and retry. Let me know what happens. As far as pressure relief opening and emptying the water heater, and your sure it's not a faulty pressure relief valve, then there's 2 things to start with checking. 1st, does the water seem extremely hot, thus a possible faulty thermostat &/or ECO . Secondly, if the incoming water pressure is too high, that will also cause it to leak bad. Try installing a pressure regulator (usually 40 psi.) at your hose connection. Let me know what you find.

Make sure propane is on and getting to your stove burners ok, first, then try switching it back on. If it fails to ignite, shut switch off and try a couple of times, if still no ignition, get back to me.

overheat stat , does it come back on with reset ?best of luck