Plumbing, Heating and Pool Repair Guides

AO Smith ProMax Water Heater Troubleshooting

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WeT HeaD KnowledgeIf you own an AOSmith ProMax GPST-40L Water Heater and are having problems with the way it is performing I’m sure the last thing you want to do is spend your hard earned money hiring a technician to repair it. Thanks to this constantly evolving, technology oriented world you have access to this very handy troubleshooting and repair guide. This guide covers many possible problems that could occur, such as: Temperature problems, noises, odors, leaks etc. If for any reason you feel as though you cannot safely perform these (or any other) repairs, please contact a professional technician.

PROBLEM: Water leaks.

SOLUTION: One of the causes of leaks in hot water heaters is when the hot or cold water valves, thermostat threads or other fixtures are not connected or sealed properly. You should always make sure that any threaded connections are secured and functional. Sometimes there might be leaks from other surrounding appliances or water paths so check to see if that is the case. One other cause could be condensation of the flue products, in order to correct this you should use some sort of cloth material to absorb the condensation coming from the exhaust vent (near the blower assembly).

PROBLEM: Water odors.

SOLUTION: Most of the time any odors in the water are due to high sulfate or mineral deposits in the water or increased bacteria counts. Too solve this problem it is recommended that you completely drain and flush the hot water heater and then refill it. Don’t forget to chlorinate the water as well.

PROBLEM: Vent pipe too hot.

SOLUTION: Commonly this is caused because the dilution air is too hot to mix with the flue gases or because there is not enough of it to mix with the flue gases. You should make sure that there are no obstructions internally or surrounding the air intake at the draft hood.

PROBLEM: Yellow flame

SOLUTION: The correct color of a flame for a water heater should be blue-ish, if your flame is yellow you should try cleaning the burner heads or ensure that there are no blockages in the air intake or exhaust venting in the bottom base pan.

PROBLEM: Not enough hot water

SOLUTION: First make sure the unit is plugged in and that the switch is turned to the “ON” position. If you can’t turn the unit on, make sure the electrical outlet you are using is working properly. Sometimes when the water is not heating up it could be a problem with the thermostat, in which case you will need to either check that it is wired correctly or replace the thermostat. Before you go to that extreme though, check that the temperature control knob is at the appropriate level. Another possibility is that the control harness or the blower motor might need to be replaced. Check to see if there are any leaks in the hot water connections as well as the external fixtures. Also be sure that the gas pressure is at the correct level, if it is too low it can cause the water to become cold too quickly.

PROBLEM: Reverberation or sizzling noises.

SOLUTION: Generally the reverberating type noise could possibly be caused by excess dirt at the bottom of the water heater tank. If this is the case you should try completely draining and flushing the unit and refilling it with chlorinated water. If you hear a sizzling noise it could be because of condensation dripping on the burner heads. Refer to the section on “water leaks” for instructions on how to fix the condensation.

43 Comments

  1. My A.O Smith Promax hot water heater is making loud grinding, grating noises dozens of times a day (and night). It is brand new and installed in a top floor penthouse (12th floor). Technicians have been out 5 times and nobody can figure out what is causing the noise or how to fix it. Can you help me?

  2. the water hearter is 2007 and satop working If you turn it on i tries fivr4e times and shuts off.
    work for week stop for two days/ work 5 days stop 2 days.
    tyhnaks
    Comerciam promax.

    • Same here I have replaced everything and still goes on. works for a couple days then back to the same old crap starts stops starts stops HELP

  3. Our water heater quit heating. What do I do next? I don’t see any external knobs, or switches, is there a “reset” button anywhere? I have a A.O. Smith Energy Saver (typical)hot water heater (cylindrical desing approx. 4ft tall)
    Heats for a 4 bedroom house in Florida. Thanks

  4. i have 9 units model gvr40-100 5 years old and 3 of them are not working anymor they loock new no leaks they stop working, if i turn them on the water heater will work till the water is hot and then it will turn of again what can i do

  5. WE STARTED HAVING TROUBLE WITH OUR A.O.SMITH HOT WATER HEATER LAST WEEK, THE PIOLT WOUND NOT STAY LIT. FINALLY AFTER RESEARCHING TROUBLE SHOOTING, THERE IS A FILTER UNDER THE AJUSTMENT VALVE POPPED IT OFFAND VACUUMED ALL UNDER THE UNIT AND CLEANED THE FILTER. lIT THE TANK AND NOW NO PROBLEMS, GUESS THE CLOGS UNDER THE TANK WAS BLOCKING OXYGEN NEED TO KEEP THE PILOT ON. 4 DAYS GOING A-OK

    • krlong:

      I’m having similar issues with my AO Smith hot water heater. Pilot won’t stay lit. It’s a relatively new heater, 2007.
      Where did you find the filter? Have not located it.

      Thanks.

  6. krlong:
    I have a finicky A.O. Smith hot water tank too. Is yours still working after vacuuming and cleaning the filter?? If so, I’d like to try your method but I am not sure where to look. You mentioned you popped off a filter located under the adjustment valve? Where is the adjustment valve? What does it look like?

    Thanks!
    hL

  7. AO smith Promax gas water heater-It worked fine this morning this afternoon I turn on the kitchen sink and no hot water! I go directly to the water heater and the drain valve is dripping water. I turned off gas and all connections to the heater. I am drying all the water that leaked and trying to figure out why the valve is leaking there is no handle to it! Do I need to call a professional right now or look for the problem myself?

  8. I have a AO Smith with power vent that is so loud that your cannot talk to any one near it…is it the motor or the flu rattling around inside??

  9. I don’t know this is the symptom of leak or no but there is 1/3 full water in the pan on the bottom of the heater.
    Is is normal?

    Thank you for answering in advancer.

  10. The pilot light went out on the hot water heater in the rental unit. I followed the instructions but the pilot would not light. The first time I tried I saw the spark but thereafter no sparks are produced when I push the pilot ignitor button. Whats the problem? By the way, just to make sure I didn’t accidentally shut the gas off, the shut off valve is marked “s” and “o” which position should it be in for the gas to flow?? What do these letters stand for?

  11. The AO Smith Promax water heater model GNR 40100 started having knocking noise after a year and now it’s gotten worse after two years. It’s been flushed 3 times and I even had a plumber come look at it and they can’t figure out way other than the heater is defective. HELP!!!

  12. my hotwater heater pilot keeps going out. I can restart but it only lasts about 10 to 15 mins. before going out. What do I do to fix the problem?

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