Intermittent start problem with Bosch front load clothes washer


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Old 02-24-19, 08:42 AM
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Intermittent start problem with Bosch front load clothes washer

I have a Bosch Nexxt 500 front loader, WFMC3301UC/09. When we go to start a load, the washer control panel sometimes does not light up at all, so the washer will not run. If we just leave the cycle selector knob where we put it the panel lights up in maybe 30 seconds to a few minutes, and then we can start the washer. I swapped out the main control board with a used (supposedly good) circuit board and it fails in exactly the same manner.

I'm wondering if one of the sensors or devices that connect to the main control board has an intermittent fault and when it fails it prevents the machine from powering up. I don't have much of a schematic but the things I see connected to the main board are the water heater element, negative temp coefficient sensor, water level pressure switch, and motor control board. Are any of these prone to failure?

Only once has it thrown a trouble code and that was during a wash cycle: E04 (door control broken; faulty triac or control module). Several months ago we had a problem where we weren't able to open the door after the washer completed a cycle. I replaced the door interlock module and that fixed that problem. The E04 code occurred after the door interlock module had been replaced.

What should I be checking? I have a digital multimeter.
 
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Old 02-24-19, 02:33 PM
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Bosch is always a hard one to diagnose. Trying to think if I have run into your problem. If I can think of something will post it.
 
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Old 02-26-19, 10:20 AM
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Interference Filter??

No takers on this one, eh?

So this washer behaves like it's not getting any power when it won't start up. I took off the top panel and traced the power wires that feed the main circuit board (the one with the LED display and the push buttons). The only thing between the power cord as it enters the back of the washer and the control board is the RF interference filter. Do these things fail intermittently? I see no damage to the wiring harness.

Right now I've got my multimeter plugged into the output of the filter and of course it's showing line voltage (120V); this problem is quite intermittent. I'm thinking of plugging an old analog electric clock into the filter to see if the power drops out over a period of days or weeks by comparing the time with another clock.

Any feedback would be much appreciated.
 
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Old 02-26-19, 01:00 PM
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Never seen filter go bad. Plenty of user interfaces and control boards, Bosch are hard to get info for, We had a tech center to call for help. Retired now so can't get any info for you.
 
 

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