Honeywell Water Heater Thermostat Woe – How I Fixed It


I heard a scream from my wife in the shower, “No hot water! No hot water! What’s going on?!” Not good. This was 10pm two days ago. My first thought was that the water heater pilot light went out, based on my past experience. What else could it be? I checked that AO Smith Gas Water heater in the laundry room right away. The water heater comes with a sophisticated, advanced Honeywell Water Heater thermostat/valve that provides continuous monitoring of the water temperature and turning on and off the gas accordingly – all without battery. It uses a “thermopile” technology that converts thermal energy into electrical energy. It’s composed of serveral thermocouples connected in series to create roughly 350 mV of energy. What a nifty device!
honeywell-module

Except when it’s not working.

I first tried resetting the module by turning it to off and re-start the pilot light by turning the dial to “Pilot”, holding down “Pilot” and push the spark igniter. The system kept coming back with 4 flashes. Based on the “Status Light Code,” it means “Temperature Exceeded.” It made sense as we had a heat wave recently. So I figured the system should reset itself once the over temperature condition goes away. I kept resetting the system without much success to get the gas burner to turn on again.

I googled around and came across this website by Tyler Tork. Wow, so many people had the same problem dating back to 2013. The problem is that the microcontroller inside the unit remembers the last “over-temp condition” and would not forget it. The recommended fix is to disconnect everything from the module for an hour and let the power dissipated to “flush” out the memory.
honeywell-module-labels

That sounded easy. I tried disconnecting it for 30 minutes. No go. 60 minutes: No go. I left it disconnected for overnight. Still no go. I even flushed some of water out to get the sediments out as it’s a source of heat barrier that contributes to overheating.

One of the people commented “shorting” everything on the little printed circuit board to really “short circuit” the memory cell, most likely the big capacitors. And that’s what I did, I figured I have nothing to lose as I would need to replace it if it didn’t work. So I removed the PCB (printed circuit board) from its housing by unscrewing the torx screw and snapping the PCB from the housing. Then I took a sheet of aluminum foil (an electricity conducting material) and touch all the various solder joints (silver-looking blobs) especially the big capacitors, which are the energy storage devices. See figures.
pcb-component-side
Honeywell PCB Bottom Side
Then I put it back to its housing and put everything back to its original positions. Turn on the pilot and hit the spark lighter. I first saw the LED flashed 7 times, which means “Gas Controller Valve Failure.” Doesn’t sound good. Then I proceeded to dial it up to temperature setting A. Immediately, the burner turns on and we have a lift off! After a minute or so, the LED started blinking once and paused and blinking once again. This means “Normal Operation.” We’re back in business now. I just saved $110 (Walmart’s price) for the module and enduring days of suffering through cold showers and complaints from my family members. Viva DIY!

11 thoughts on “Honeywell Water Heater Thermostat Woe – How I Fixed It”

  1. I just tried this tonight.
    Unplugged the red & white wires, took the plastic cover off. in plugged the ribbon cable from the circuit board. I then rubbed and patted the printed circuit with aluminum foil. Put it back together and it lit, and fired right up. Yes, now it was blinking 7 times. I turned it off.
    Unplugged the red & white wires until the indicator light went out. Plugged the wires back in, lite it, turned the temp diel up, it fired up and now its not blinking the 7 anymore just the one, flash, indicating ok.

  2. I took the circuit board out. Then I dabbed / rubbed
    A ball of aluminum foil over the entire circut board on the solder side. Making sure I hit every solder joint.
    Put it back in and it fired up.

  3. I didn’t get the 7 flashes. Actually, it started flashing 4 again! But, the pilot did light, I turned up the temp setting all the way and waited for about 1 or 2 minutes. Then, I heard the burner light up and the lift started to flash 1 for normal operation. Hopefully this fix will last! Thanks for the tip and making the video!

  4. Tried this procedure. Still not working. I did get the correct flashing light temporarily. Guess I’ll try again and let it set longer

  5. Quick Reset: I was getting the 7 flashes. Researched it and found that a common problem is someone doing painting in the vicinity of the water heater (yes that was us). Unpublished RESET: 1) Turn switches to off (blower switch, and controller switch). 2) Unplug from wall for 10 secs. 3) Plug back in. Turn blower switch on. 4) Turn controller switch on and immediately rotate temperature knob all the way to MAX LOW, then all the way to MAX HIGH, and repeat seven times (or maybe more). BLAMB!!!! Right before your own eyes the furnace mower kicks on and the water heater lights up a few seconds later! So nice 🙂 (Rheem 50 gallon with that Honeywell controller you have a photo above). 2017-10-23

  6. Mmmmm, not sure if this is a proper reset method. But I’ll approve this comment and let other brave souls to confirm.

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