This document was last updated on 12 March 2010. Whirlpool / American Water Heater Company / US/Craftmaster Water heater Company 50-Gallon Energy Smart model EE3Z50RD055V Lifetime Warranty electric water heater Therm-O-Disc (TOD) electronic control board repair / troubleshooting: ****** News! In early March 2010, I finally found the alternate control board, the so-called UTEC (aka HSCI), on eBay. At first glance, the UTEC board is of much simpler design than that of its Therm-o-Disc cousin. There is a single 5.1-volt zener diode. The zener regulates the supply voltage of a 28-pin microcontroller device, which is manufactured by Microchip Technology, Inc. I have only begun experimenting with this UTEC board which was manufactured during the second week of 2004. One striking difference between the two control boards is that the UTEC board has a small control power transformer which isolates the control electronics from the sometimes harsh environment of the incoming 240 VAC power line. This feature alone helps to make the UTEC control board more reliable than the Therm-O-Disk control board, in my opinion. More later. Experiments continue! ****** Consider transient protection, connected to control board 240 VAC input terminations. Consider ventilation and air filtering of control board housing. Insufficient 48VDC coil bus level may cause intermittent operation and failure of relays due to severe arcing of their contacts as they cycle on and off repeatedly at times when they should be solidly on. Also, when the 48VDC relay coil bus malfunctions, the 5VDC bus, which powers the microcomputer device at U1 and the CMOS dual op amp at U2, is adversely affected, possibly resulting in complete loss of control and diagnostic-reporting functions. American Zettler AZ2270-1A-48DEF relays or Tyco P&B T9AV1D22-48 relays 'Must-operate-voltage' of both the above electro-mechanical relay models is 36VDC. sales@relaycenter.com The value of C2 on my original TOD control board measured only 0.7 uF, which presented an Xc at 60 Hz of 3789 ohms. It was supposed to be 1.0 uf and it was labeled as such. Question is whether it was always a 0.7 uF cap or has it degraded over time. I have replaced the original X-Class cap at C2, using a CDE type DME 1.0 uF, 630 VDC, 250 VAC device, bringing the attendant Xc at 60 Hz back down to about 2650 ohms. This causes the 48 VDC relay coil bus to run at 42 VDC with three out of four relay coils energized (one of the normal conditions), at a L-L input voltage of 239 VAC. The six 1N4738A zeners failed, becoming quite hot and short-circuiting at some time, I believe, during the overall board failure. This heating is evident from moderate board scorching beneath each zener. I plan to use the original TOD board as a spare, so I have ordered a few replacement parts and have been installing them as parts arrival and time have permitted. Test fixture: 120/240 volt transformer http://www.voltage-converter-transformers.com/deluxe-step-up-down-transformer.html Female stab-on connectors. Two independent 50K ohm rheostats for simulating resistance span of the two thermistors, plus switches for simulating open thermistors. One possible four-pin mating connector for J1 is the 2mm AMP CT, Tyco Electronics part number 2-179694-4 . Three additional lamps for visual indication of (K3 & K4) status; K1 status; K2 status. I have been successful at manipulating simulated thermistors (rheostats) to obtain, one at a time, each of the five blink sequences (one, two, three, four, and five blinks),as well as the steady 'on' glow, from the onboard green LED at 'DS1', on the original TOD control board which I removed from my water heater on 16 FEB 2009. This means, of course, that, given nominal control board power supply voltages, the ST Microelectronics ST62T01C6 microcomputer chip at 'U1', and all of its supporting devices are still functioning normally. I am curious, though, as to why there's a little spot of white paint on top of the microcomputer chip on the original TOD board, while the little spot of paint on top of the microcomputer chip on the replacement TOD board is red. Could it be that there have been changes made to the chip's program code along the way? The devices which were destroyed on my original TOD control board are relay 'K1', and the series string comprising six 8.2V, 1 W zener diodes at 'D9', 'D10', 'D11', 'D12', 'D13' and 'D15'. These failures on the TOD control board did not cause fault current flow sufficient to trip the water heater's associated 2-pole, 30-ampere circuit breaker, which is located within our home's 200-amp-service breaker box. I have also witnessed erratic operation of undamaged relays 'K2', 'K3', and 'K4' as the '48VDC relay coil bus' on the same board varied from 30 VDC to 39 VDC, while my electric utility supply varied from 230 to 242 V L-L. This was done prior to my discovering that the value of C2 measured 30% low. Fortunately, the replacement TOD control board continues to function normally since I installed it on 18 FEB 2009. But, it causes me to wonder about future availability of the TOD control boards when I see them appearing in eBay ads. The latest I have seen at eBay ends on 03 May 2009 and I found it by searching eBay for: Therm O Disk which was, perhaps, an unintentional misspelling of the item. Schematic: w.i.p. Additional interest: Procure the optional 'UTEC' control board and learn its secrets as well. It would be useful to know whether failures occur more often in the above-described 'TOD' control board, or in the 'UTEC' control board, either of which may be utilized in the subject water heater, as pictured in the troubleshooting guide found at: http://www.americanwaterheater.com/support/guides/es.pdf My email address: n4qa@hotmail.com