Intermittent hot water

Whether using electric or propane that water heater needs 12V DC to properly function
Electric & propane both use the circuit board.

12V DC comes from ON/OFF switch to circuit board via WHITE (electric) or ORANGE (propane) wires
Then 12VDC goes from circuit board to T-stat via BROWN wire (top connector) then thru t-stat and thermal fuse (clear tubing) and back to circuit board via BROWN wire (bottom connector)

12V DC then comes from circuit board to ECO via RED wire then to gas valve solenoids and to ground via Black wires
When using electric the 12V DC voltage is just milivolt signal to ECO & gas solenoids
12V DC triggers a relay at electric element to allow 120V AC to element

ANY disruption of 12V DC from on/off switch to ground at gas solenoids will shutdown operation OR not allow any operation.

When using propane you should get a spark at burner almost immediately when you turn switch ON (provided water is cool enough <110*F)
Then you should have 12V DC on gas solenoids for 6-8 seconds while spark is going on.

Check terminals/contacts at ECO.....loose/dirty/corroded NO DC current.
Doesn't take much to disrupt 12V DC

If no sparking then problem is in circuit path from/to circuit board on BROWN wire (for non working electric and/or propane)

Pull connectors on circuit board..check pins (not bent etc) and clean contact surface on board with an eraser
Pull spade and pin connectors on t-stat and ECO....make sure they are clean and tight
Check t-stat and ECO making good tight connection with tank wall
Pull spade connectors on gas solenoids ...make sure clean/tight


Does T&P Relief Valve drip......dripping can cause issues with connections on T-stat/ECO


When you get it to heat water.......that mixing valve on backside can be an issue also.
Hot water out form water heater can get clogged with scale/crud and then only warm/cold water will flow

XT Model Manual



Wiring diagram

EXT model. That means you have a MIXING valve that mixes extremely HOT water with cold to produce 16 gallons of hot water. IF your problem is LACK of consistant HOT water, then your Mixing valve is BAD. Go to the pressure relief valve(Pop Off valve). Open it and see if you have scalding water. If so, your Mixing valve is bad. Doug

Thanks to both of you. When it works, i have no problem with the hot water, so I think the mixing valve is not an issue. I was thinking it could either be the eco tstat or the circuit board.

Unplug the connectors and spray with WD40 and put them back together. That will solve 99.9% of the connector problems. It is quick and inexpensive and has worked for me on just about anything electrical.

Thadley wrote:
Thanks to both of you. When it works, i have no problem with the hot water, so I think the mixing valve is not an issue. I was thinking it could either be the eco tstat or the circuit board.

Test/measure the 12V DC circuit until you locate WHERE it isn't....