Plumbing, Heating and Pool Repair Guides

Bosch 1600P Tankless Water Heater Troubleshooting


WeT HeaD KnowledgeIf you own a Bosch 1600P Tankless Water Heater (with Pilot Ignition) and have been having trouble with your unit I’m sure you have been dreading the idea of calling an expensive repair technician. This article outlines many of the possible things that could go wrong with this particular hot water heater and the causes and solutions that will hopefully resolve your issue(s). Problems that may occur include things such as: leaks, temperature regulation problems, ignition failure, low hot water pressure, air blockages or even noise problems. As always, if you feel that you cannot safely do these repairs on your own than please call a professional.

PROBLEM: Yellow flame.

SOLUTION: This usually occurs when the burners are dirty or when there is a blockage in the air intake or ventilation system. Make sure that the gas pressure is operating at the appropriate level (check your manual for what the level should be).

PROBLEM: Water not getting hot enough.

SOLUTION: First make sure you are using the correct type of gas. Ensure the flow is within the limits of the heater’s capacity. Check to see if the gas control button is set to the “flame 3” position and that the temperature knob is turned to the appropriate setting.

PROBLEM: Low hot water pressure.

SOLUTION: Make sure that the tubing and connections outside of the water heater itself are free of blockages. Be sure that there aren’t too many taps open at one time as this will weaken the overall water pressure. Check to see that the water pressure coming into the unit is above 30PSI. You can also test the flow rate of the whole unit by doing the following: 1. First shut off the cold supply and disconnect the hot water outlet. 2. Put a bucket underneath the hot water outlet to catch the water. 3. Open the cold supply and take a reading of the pressure flow. 4. If the temperature knob is all the way clockwise the pressure should be 2 gallons per minute and if the knob is all the way counterclockwise than the pressure should be 4 gallons per minute. If you don’t get those pressure readings you should try cleaning the inlet filter screens.

PROBLEM: Water is too hot.

SOLUTION: If the gas control button is on the 3 flame position lower it to the 1 flame position and turn down the temperature knob if necessary. Make sure the inlet filter is clean as well as your showerheads and faucets, increase the flow rate if you need to. If the mineral level in the water is too high it may restrict the water flow and in turn cause the water to boil and create higher temperatures, if this is the case consult a professional.

PROBLEM: Pilot does not light.

SOLUTION: Make sure the pilot assembly is not blocked, clean or replace the pilot orifice if you need to. Check to see if there is a spark when you press the gas control button, if not make sure the wiring is functioning and connected properly. Ensure that all gas shut off valves are in open position. If there is no gas check that the regulator is in the upright position, the arrow on the back of the regulator should point in the same direction as the gas flow. Lastly, make sure there is no air in the gas flow. If this is the case you can bleed the air out of the gas flow by holding down the gas control button while holding the pilot igniter button.

PROBLEM: Burners do not light with water flow.

SOLUTION: First make sure the pilot is lit. Make sure that the gas control button is between the 1 and 3 flame position. Check to see that cold water intake is connected to the correct side of the unit. Open all hot water taps and check them, if water is flowing you have a plumbing crossover. Make sure the hot water flow is high enough. You can do this by putting a milk jug under a hot water faucet and if it fills in 30 seconds or left the flow is fine. Check to see if there are any blockages that are external to the hot water heater and that the inlet filter screen is clean.

PROBLEM: Pilot lights but goes out after you stop pressing the button.

SOLUTION: Firstly, make sure that when you are lighting the pilot you are holding the gas control button for atleast 20 seconds. Check to see that the flame is the appropriate color (blue) if it isn’t you may need to clean the burners or filters or check the gas pressure. If the heater is attached to a power vent be sure that the safety spillage switch is working correctly. Check the wiring on the pilot safety circuit as well as the electromagnet. If there is corrosion you can clean the sensor connections with light sandpaper. Also make sure that the electromagnet is properly screwed into the thermocouple. Ensure that the thermocouple is operating properly by measuring the millivoltage to the ground. The appropriate reading should be 24mVDC or above, if not you may need to replace the thermocouple.


  1. This is the 2nd time I have used this method of contact…we have called the # over 3 dozen times, we purchased a bosch hotwater heater 3 years ago and it has never worked properly, I have had 2 different plumbers here spent over 2 grand having this thing worked on, as I could never get anywhere on the tech line but put on hold and then disconnected, Never had consistent hot water, replaced 3 parts, now no hot water at all…this hotwater is a nightmare and we regret ever having purchase a Bosch product

  2. The Pilot light, but burners will not come on. Following all the troubleshoot step lead me to replaceing the Electric control box 190.00 so I order the box and a pilot orifice 4.00. Once I recieve both parts I replace the pilot orifice first I did a operational check finding out the sparking plug was shorting out 28.00 replacement cost. I found the short because the was lite was turn off so you could see the short when the system was tring to start.
    Swap out the sparking plug still no JOY. I exam the sparking you have to insure the jump correctly across the spring and the bar that start the burner. moving the coil around so it sit just right fix the issue.
    sadly I hope to beable to send the box back however the a stock fee of 25%. I enjoy the tankless water system But work on the system is the hard part. By the way you need to follow the trouble shooting guide that Bosch has writen that did help.
    I hope this help you.

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