Water heater: warm, not hot

Which model no?

Anode has nothing to do with heating the water. First, check the valve positions at the back of the WH. Sounds like one or more are in the wrong position. If there all correct, then you need to check power. Are you running on gas or electric mode?

Bypass is not completely closed.

Check the outdoor shower if you have one.

warm on gas or electric?

As posted ..anode rod has NOTHING to do with water temp. It is a sacrificial rod to provide protection for the STEEL tank Suburban uses and help minimize corrosion.

Water temp is a function of HEATING the water
Propane has its own set of t-stats to control temp of water
Electric has its own set of t-stats to control temp of water (if WH has electric)
Both control water temp to 130*F/Normal

IF the corresponding normal t-stat FAILS then water can be over heated. Hi Temp T-stat/ECO shuts down heating at 170*F
Typically normal t-stat issue result in too hot or NO heating----not warm heating

So water S/B HOT inside WH TANK and output temp is getting diluted by Cold water mixing with the HOT out.
Bypass valve cracked open....water from cold inlet goes directly to hot outlet
Shower (inside/outside) not shut off via cold/hot knobs but just with 'button' on shower handle---cold/hot mix inside shower faucet.

Either one...result is luke warm water. Can be bursts of HOT when first opening a faucet then it goes warm

Cold mixing with HOT...check all valving etc.

Continued from https://forums.goodsamclub.com/index.cfm/fuseaction/thread/tid/29421218.cfm - is a suburban, the three valves are set to open, the sitter outside was properly turned off with the knobs, and also the button on it is off. Thanks for the explanation about how the tstats work, makes sense. I'm using gas, not electric (didn't know it ran in electric too, thanks) let's see, Oh wait, the bypass needs to be closed! That's why I bet. Thanks! That would make sense why it cycles between hot and warm...:-) much appreciated