CT Midi - Unreliable Starts

[cdwaund]

I have a 2014 built CT Midi (499605).  I'm a hobbyist - it's had a reasonably leisurely life - but used routinely - hasn't sat unused for long stretches or anything.

Recently it periodically refuses to start either in manual mode, or in auto paired with a tool.  Some days no issues, but others no go.
Common symptom when it won't kick off and run is a short burst as it starts to spin, then goes does dead.

In auto mode the tool always has reliable power.

Based on reports of friendly support, I called Festool Service but only got instructions to send it in, no troubleshooting help.

Reading threads on the board, I went ahead and opened the case hoping for loose connections or something obvious -- but no joy.  Of interest to me is that this vac is somewhat unique that the switch and control board are separate and non integrated (?).

So, my current thinking is #1 replace the electronic control board, #2 replace the switch, #3 what about the motor brushes?  #4 wave the white flag and send it in for repair.

Anyone have sage advice to share?  All inputs, including experience/cost with similar repairs through Festool Service, are appreciated.  Both the switch and control board appear to be called "conversion kit" on the online parts list, with a cost of $105 each.

Thx.  Dane

 

[AlexThePalex]

Anyone have sage advice to share? 

Maybe start with checking if the cord isn't broken? Since you have no problem opening the vac yourself, just replace the current cord with another one. With the symptoms you describe the cord is the first thing I would check. I think maybe 90% of broken tools I encounter is the cord. Wires break easily.

Doesn't sound like it is the brushes, when they go the entire vac stops working and nothing intermittent. Also a 2014 is too young for the brushes to be worn unless it ran 10 hours each day. I had a Mini from 2006 and the brushes were still good.

If the cord is alright, next thing to check is the electronics board. Just take it out of the loop, connect the cord directly to the motor. If the motor works as it should, then the problem is in the electronics board/switch combo.

I doubt it's the switch, they are very sturdy and closed off. Nevertheless, sometimes contacts can get oxidised for no apparent reason. To find out if it's the switch, disconnect it from the board and figure out which contacts on the board you have to connect to each other to get the vac working as it should.

So, by eliminating each part one at a time, you can check where the problem is.

 

[TwelvebyTwenty]

Have you tried it in a different electrical outlet?

I have had a similar(ish) issue with a Bosch Vac where it was powering the tool but the suction on the extractor was terrible. I thought the extractor was on the way out, but turned out the outlet I was using had a wiring problem and for whatever electronics reason that is over my head, the power was being delivered to the attached tool as a priority rather than the extractor motor.

 

[imaginarynumber]

I had a similar problem with a CT22. Initially, I used a volt pen which showed that the live in the lead was OK. I stripped the machine down, only to discover that it was nothing more than a break in neutral in the lead.