Water doesn't stay hot PowerStar AE3.4

Shower heads have flow limiters installed in them. This means the water heater cannot sense the water flowing and therefore it wont come on. Take the shower head off and look in the end for a piece of plastic that is in the swivel. Remove it. Then put the shower head back on.

It should be producing hot water at the temp it was set at such as 120-140 degrees. If it is exceeding this one of the safety devices maybe disconnecting it. Thermal control might need some servicing. See what temp it's set at then put a thermometer on a near water outlet to see what's going on. Good luck.

Problem might be crossover from failed single-handle faucet cartridge:
http://waterheatertimer.org/Crossover.html

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What happened to the screws from the old terminal strip?
If it is a different size you need to drill new small holes in the box (not the tank or pipes) and attach it with self tapping screws. Make sure each wire of the unit matches the same wire being connected as the original connections.

Since you have hot water at all the other fixtures, the problem lies in the sink, not the water heater. It could be that the sink is farther away from the water heater than the other fixtures. It would take longer to get hot water.

try bleeding that section of pipe. or the whole system if not.

Ok, sounds like a flow sensor issue, is your house water pressure steady or does it fluctuate? The sensors on these seem to be a common issue and this model has many issues with heating. take care

it sounds like 1(or more) of the motorised valves arent working.find the valve and make sure you are getting power to it via a tester,if so then it probably needs the head on the motorised valve changed

If I were you I would look into a insinkerator, they are more reliable and more efficant, and have a better customer support, and warranty

I found a way to get warm water in the shower, but I'm not sure it qualifies as a solution. After trying everything else I thought that maybe when I was feathering the faucet in the shower toward the cold side so I would get warm water that at a certain point it blocked the flow on the hot water side enough so that the sensor in the hot water heater sensed there was no demand in the line and it shut the water heater off. To test this, I went to the kitchen and turned the kitchen sink faucet all the way to the hot side and then turned it on so that I got a small flow of water. I waited for the water to get hot to be sure the hot water heater was working. Once it was hot, I left it running to keep demand in the line and then I went to the shower and turned the faucet on. When the water got hot I started feathering the control towards the cold side and soon I had warm water. So I think I'm right in that the sensor in the hot water heater was shutting the water heater off when the demand in the shower was lowered to a certain point when I was trying to adjust the water temp in the shower.

So now I can get warm water, but it means I have to leave the hot water running at another fixture in the house to create a false demand in the system so the hot water heater doesn't shut down. Is there a way to adjust the senor in the hot water heater so that it will stay on when I'm using the shower only, so I don't have to waste water by running another faucet when I want to take a shower?