Have a titan n-120 tankless water heater that gets very hot at sink but not hot at shower.

SOURCE: Titan tankless hot water heater will not go off standby.

There are FAQ's at the following location:

http://www.titantanklessheater.com/page/1227557

Could be a few things. Most common are reversing the water flow (putting your cold water input into the units hot output instead of the other way around) or not bleeding the air out of the unit (running water for a minute with the unit off) before using it. Could be a bad flow detector switch or an internal malfunction as well. If you review the link above and my tips and don't find anything then contacting the company is probably your best option.

SOURCE: We have a powerstar 125

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

SOURCE: I have a Titan N-120

I have not worked on this model of heater. I have several trouble shooting tips for you to try. This is the approach I would use if this were my heater. But first, you say it lights up for hot water then you ask about elements. Is this electric or is this gas fired?

If it is gas fired, it is lighting (a burn sequence) and not heating, I would suspect a flame sensor problem. The fire comes on but the sensor cannot 'see' it so the safety turns the gas valve off. If it is gas fired, there probably is a electronic ligniter ... I would take a look at that to make sure it is lighting. Normally, this is a strip of metal that heats up red hot or a sparking device. Look for the red light inside near the burner or listen for the spark.

If it is electric, I would turn the power off and with a volt/ohm meter, I would measure the resistance on the elements. Set your meter to oHm for this reading. You should read "short" if the elements are good. (Short is the same reading you will get if you cross the probes (direct contact one to the other)) If there are two elements, check both. This is step one in proving the elements. If they both check good, turn the power back on and check the voltage (set meter on 250 VAC or higher) Place the probes on the screws that hold the wires to the elements. Now then, if you get a reading (Is this 110 VAC or 220 VAC - read the volts on the meter) Your thermostat is fine. To prove this, turn the thermostat off and the voltage will drop to zero. If there are volts and still no heat, I would suspect the elements are indeed faulty and should be replaced.

I hope this answers your question. Thanks for your visit to FixYa.com today.

SOURCE: I have a titan 120

Replace the element it is shorted out.

Testimonial: "I ordered one Monday. Just wanted to make sure I was doing the right thing. Thanks"

SOURCE: No Hot warer frpm our

Hi,
The water is dripping from the connection because the connection has cooled as a relut od the hot water not keeping it expanded...

Now... the tank may not be heating for many reasons....first check that you have power going to the heater...
Then make sure the reset button has not tripped...if it continues to trip then you have a problem... usually with the thermostat...
If that is not tripped then the thermostat could be bad...and not sending power to the heating element...
If you have power to the heating element and no heat then the element burnt out...

heatman101