Enviro M55 Troubleshooting - Stumped

I've been chasing trouble with an Enviro M55, and I even had local dealer come out to diagnose. We still don't have it.

M55 (free standing) was running great until one day it did shutdown cycle while still plenty of fuel. Blinked 3 as if it was out of fuel.

For a while it restarted great and then did shutdown after 15 minutes startup. Auger feeding fuel fine. Combustion-Exhaust blower running good. Igniter starting the fuel just fine. Great startup and good burn but then shuts itself down.

This problem sounded exactly like the M55 could not confirm "fire" after startup. So ran test of bypass exhaust temp sensor. But igniter (maybe auger too) was then intermittent. Sometimes when successfully lighting a fire it would shutdown with blinking 4 but other times 3. Other times the igniter and auger would not run, but some vibration to the stove would start igniting (like a loose connection or failing switch?). Made sure stove was clean. Checked connections were secure. No improvement.

Tried bypass of vacuum switch with no luck. Lots of blinking 4.

Had service call from nearby dealer and after a lot of tests (that didn't work) they bypassed the High Temp as a test and got the stove running. They concluded High Temp Limit switch had failed. So we thought the repair was done. A couple hours after leaving the stove started shutting down with blinking 3 OR blinking 4. And now it won't run auger or ignite ... even with the High Temp switch temporarily bypassed it's blinking 4.

Weirdly we started with this stove running great! Hard to imagine more than one sensor / switches failing all at once but we have been chasing this problem in circles and can't identify a (single) fix.

Ssyko said:

Is the stove plugged into a quality surge protector? Any power outages or brown outs?

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I wouldn't call it a quality surge protector actually. That needs to be fixed. But no power outages or brown outs that anyone here has noticed.

stovelark said:

Did you check the ribbon connections to the motherboard? Could be a flaky MB too. Is the exh sensor (proof of fire switch clean too)? I would change that too. Good luck with her.

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Ribbon to board looks good. The loosest connections I found anywhere was exhaust temp sensor disconnects; those were sloppy loose to begin with but I tried to correct that.

I just revisited bypass on the High Temp again and at first there was no ignition -- but I fiddled with the wires behind control panel board and it came to life with good startup cycle and good fire. I'm watching how long it will keep running.

Looking like there could be loose wire somewhere near High Temp disconnects or failing lid-open switch.


*** Update: ran well for 90 minutes to 2 hours. Just checked and found fire OUT but control panel still showing normal "on" heat level 3. No trouble code on control panel. Plenty of fuel in hopper. Burn pot did look low on fuel (couldn't see well enough to say it was empty.)
Tried restarting and a few minutes later found trouble light '4' that cleared immediately after moving wire running from lid switch, down near where it connects with faston.

SOLVED!

I'm writing back with a solution. This case might be interesting because after a lot of frustration, mystery, and investigation the actual cause was different from what anybody including me had guessed.

I discovered that the wires running between the lid and motherboard had sagged down and been periodically resting on the rotating blower motor. Over time the insulation had been worn off the wires and some of the conductor itself was getting eaten away from the abrasion. Replacing the damaged wiring worked perfectly.

The problem was practically invisible at first. Facing the wires, the damage was done to the back of the wires, and the front of the wires looked completely normal and undamaged. The local stove repair guys couldn't find it and recommended I start buying replacement parts and trying those (starting with the thermal switch). And it took me hours of head-scratching to find, which was more time than they could spend on it.

I paid for a replacement blower motor $$$ on this machine due to noise -- bad enough to drive people out of the room. I probably won't find out in this life if the real problem with the blower motor was this pair of wires sagging down onto it.

Maybe this answer will help someone else out.