Problem and flashing display on AO Smith GAHH 50

by Smith

I have the tank-type gas water heater from AO Smith manufacturer, model Effex GAHH-50. This is the high efficiency unit with the atmospheric venting and air intake chamber.

The problem is that the water heater is not working. There are "heating" and "open" flashing lights on the electronic control display, and I am having hard time figuring out the meaning, so I will try to troubleshoot it by myself and avoid calling the plumber or technician.

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Aug 08, 2019
flashing blue light
by: Anonymous

Have talked to my installer. flashes every 3 seconds. He said this is the correct flashing for AO Smith hot water heater!!!!!

Feb 07, 2015
Troubleshooting the AO Smith
by: Anonymous Jack

Electronic control display on your AO Smith water heater is a very neat feature. The "heating" and "open" flashing light indicates that the problem might be the ignition or flame failure, the GAHH-50 model reached the maximum number of retries so it is in locked out position, which is by default for one hour.

So, the solution might be easy which can be fixed without calling the plumber and if you are a handyman, or difficult which requires the technician or a licensed plumber.

If you decide to do it by yourself this is what to check and how to fix:

Check is the gas supply available to the water heater (is it on and is the gas pressure according to the recommendations). Check also the manifold pressure and if it is off by more than 75 Pa, replace the lower control.

Make sure that the voltage is also according to the manufacturer instructions which is between 115 and 125 VAC.

The flame sensor must have a good contact with the gas burner flame, the flame sensor is not dirty and covered with the deposits, which reduces its capability to transmit the electricity. Clean it if it is needed by using the fine steel wool.

Since the unit is equipped with the hot surface ignitor, ensure that it is positioned correctly to properly ignite the gas.

Also check for any damages on the ignitor's insulation, see is the resistance within the range from 1.72 to 2.4 ohm... and if it is not replace the element.

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