Weil Mclain ultra 155 series 2 Digital display dead

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I have a Weil Mclain ultra 155 series 2. I have to often reset it when it heats domestic hot water as it goes too high. Today it was flashing code E 05. I hit the reset and the entire digital display went dead. I have checked both fuses they are fine. There is power to the unit as the blower fan is working. I note that when I unplug the external transformer the blower fan is much stronger. WHen the external transformer ( 12o v / 24 v AC ) jack is plugged into the control board the fan seems very weak. The capacitors look ok but I am not certain how to test on the board. ANy ideas ?

EdTheHeaterMan

Are you the end user are are you a professional that is trying to diagnose the problem? Weil McLain tech support will tell you to get a professional that is familiar with their product to look at it.

As with anything having to do with computers, have you tried cycling the power off and back on to get the computer software to reboot. Also check to see if all the ribbon cables and wires that go from the display to the main circuit board are connected properly by unplugging them and plugging them in again. If that does not get you operational you will probably need a part. What part will be determined by a professional on the phone with WM Tech Support.

Edit: the WM Control supplement https://www.weil-mclain.com/sites/default/files/field-file/ultra-series-2-control-supplement_1.pdf indicates that you should check for 120V and a blown fuse. (see figure 16 on page 24) It appears that you have already completed those two checks. Now it is time for Tech Support and perhaps a new part (My guess is part number 383-500-190)

HVACNUT

The display has nothing to do with why it needs to be reset often, so getting a good tech will kill 2 birds. 
Do you have combustion numbers from the last service? Was there a last service?

GGross

do you have the manual? the manual walks you through this, E05 looks like a display error, then display goes dead







This won't fix your old reset issue, which is much worse. If you were resetting it because it "goes too high" that sounds like tripping the high limit. Do that a few times and there is a good chance that much more is wrong inside your boiler than a dead display board. It needs a proper service.

Karl Reynolds

If it is indeed the control board as Ed suggests, that part number has changed. It is now replaced by
383-500-665.