Hot water heater

Sorry for the late response but y'all were correct, it was the bypass valve. Got one yesterday and replaced it. I have hotter water than I've had all year!!
We are in a campground 700 miles from home so it took a while to truble shoot it and wait until Monday to find a part.
Again thank you for all your help!! Barney
PS been in the 30's the last two nights so that made the water colder.

For those that think the bypass valve is partially open or open----That would be a valid item IF it was after a Winter season. The OP has been using his unit, so how did the bypass get open or partially open??????? He has an EXT model and a Mixing valve is the most common cause of this type failure. Doug

Sounds like your bypass valve on your hot water heater is partially open.
Close it all the way.

The most common cause of "Luke warm" is use of the outside shower.. You cut off flow at the head but leave the mixing valve open. I have "Fixed" a few by simply closing the mixing valves.

THe 2nd most common is a 3-valve Bypass system and leaving the bypass valve open.

And as the third response said. If you have a mixing valve. that can do it too.

BUt I'd check issues in just that order.

I need a drink

You have a EXT. The mixing valve is bad. You can remove it and attempt to clean the minerals/calcium out of it or replace it. So, yes, you are right. It DOES mix with the cold water thru the mixing valve. 160 degree water mixes with cold water thru the mixing valve to produce 130 degree water. Doug

PS, you do NOT have a 16 gallon Water Heater. You have a 10 gallon water heater that mixes the HOTTER(160 degree) water to produce 16 gallons of 130 degree water.

https://www.amazon.com/s/?ie=UTF8&keywords=atwood+mixing+valve&tag=googhydr-20&index=aps&hvadid=241901783643&hvpos=1t1&hvnetw=g&hvrand=297869772489756071&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9027307&hvtargid=kwd-325735003851&ref=pd_sl_5u7krd5h8s_e_p37

This is where it is located.

https://www.amazon.com/Atwood-94026-XT-Water-Heater/dp/B000HDCRH4/ref=sr_1_5?ie=UTF8&qid=1539475468&sr=8-5&keywords=atwood+mixing+valve

If you have an outside shower, check to make sure its off at the knobs, not just the end of the hose.

Check the winterizing bypass valves.