HeatingCodesWeil-McLain Ultra boiler error E02: ignition failed through 5 attempts
What E02 means
Weil-McLain's control supplement and service guide for the Ultra Series 1 and 2 boilers (Ultra-80, 105, 155, 230 and 310) lists E02 as a hard lockout: Ignition failed through 5 attempts. On a hard lockout the display flashes the first digit, then an E, then the last two digits. The boiler restarts only when someone presses the RESET button on the display panel.
The guide begins its E02 checklist with a question: does a spark occur or not? The checks differ, and both lists are written for service technicians.
What the service guide lists
| Situation | Checks listed by Weil-McLain |
|---|---|
| Spark occurs | Check the ignition electrode cable, electrode connector and other connections. Inspect for insulation damage. Resistance of the igniter wire should be 1000 ohms plus or minus 50. Check the ground lead from the ground terminal strip to the heat exchanger access cover. |
| Spark occurs but no flame | Verify the manual gas valve in the boiler is open. On the 80 and 105 models verify the plastic line from the gas valve to the air inlet elbow is connected and not kinked. Check incoming gas pressure, because a gas pressure that is too high can lock up the gas valve regulator. Verify gas lines are free of obstruction and purge air if needed. Verify flue gas vent and air supply piping are installed correctly and unobstructed. Check voltage to the gas valve, about 19 to 21 volts DC during an ignition attempt. Inspect and clean the ignition electrode. |
| Further items | Check the condensate drain and trap for restriction. Clean the heat exchanger as part of maintenance. Check for flue gas recirculation at the vent and air terminations. If everything else checks out and the gas valve is powered and gas flows, replace the gas valve. |
Items such as measuring resistance, gas pressure and valve voltage are not homeowner tasks. Weil-McLain also warns of an electrical shock hazard and says to turn off power when working with wiring or replacing components.
Where a homeowner can help
Two points in the list are visible without tools: whether the vent and air intake terminations outdoors are clear of snow, ice or debris, and whether the boiler's gas shutoff is open. The guide says a restricted vent will not allow the boiler to light. If E02 comes back after one RESET, a technician should take over.
Safe homeowner checks for Weil-McLain Ultra boiler E02
- Check for a gas smellIf you smell gas, leave the house and call your gas utility from outside. Do not press RESET.
- Check outdoor vent and intake terminationsFrom the ground, clear snow, ice or debris from the vent and combustion air terminations. Do not take the pipes apart.
- Press RESET oncePress the RESET button on the boiler display. The guide says RESET should restart the boiler once the cause is corrected, but it will lock out again if the cause remains.
- Call a technician if E02 returnsDo not keep resetting. The causes include gas pressure, the igniter and wiring, venting and a restricted condensate drain.
Frequently asked questions
Is E02 the same as a flame sensor problem?
The guide lists the electrode, gas valve, gas pressure, vent, condensate and heat exchanger. It does not describe E02 as only a sensor problem.
What is the difference between E02 and E03?
E02 is ignition failure through five attempts. E03 is listed as ignition failure or a gas valve electrical problem. If E03 happens before the boiler tries to ignite, the guide points at a gas valve connection.
Will the boiler restart on its own?
No. A hard lockout needs the RESET button on the display. A soft lockout (the b codes) restarts automatically when the condition clears.
Sources
- Part 550-100-029/0810: Ultra Gas-Fired Water Boiler Series 1 & 2, Control supplement and Service guide (Weil-McLain) Covers: Weil-McLain Ultra Gas Series 1 and 2 condensing boilers (Ultra-80, 105, 155, 230 and 310). The guide is dated 2010; newer firmware can differ.
Safety note: this page is general information drawn from the sources above. Gas, combustion and line-voltage repairs belong to a licensed professional. Your own equipment's label and manual take priority over anything here. Read the full disclaimer.