CTL midi 1 wont start / Diagnostics

[Danieljerloew]

Hello FOG,

First off, I should mention that I’m not a tradesman by profession—I’m actually a custom wheelchair salesman and technician. But in my spare time, I enjoy tinkering with broken tools, and I get a lot of satisfaction from fixing them up. So far, I’ve managed a 100% success rate, and I’d like to keep that streak going!

I’m fully aware that I could send the unit to Festool for repair, but since this isn’t my primary unit, I’m not looking to have it restored to brand-new condition, which I’ve heard is Festool’s usual approach.

Recently, I picked up a CTL Midi 1 from Marketplace for next to nothing because it wouldn’t start. After a quick inspection, I found that all the controls and buttons work, and power is running through the machine since the front socket powers tools without issue.

I brought it home and disassembled the motor, to check if the problem was with the brushes, motor, or something electrical. Unfortunately, I broke the small plastic fan while removing it, as the metal pin was corroded and stuck—there was no way to get it off without damaging either the motor housing or the fan. The motor housing also broke while separating it from the bottom, which seems to have been held together with some very strong glue. No worries, though—I’ve found replacement units at a reasonable price if needed, maybe i can find the house by itself, since the motor on this unit seems in super condition, no rubbing, nothing burnt.

I connected the machine to the app, and it shows only 22 hours of runtime, with no faults detected. It’s a 2022 model, so I ran the latest firmware update, hoping that would do the trick, but still no luck.

Here’s what I’ve checked so far:

Brushes: 90% life remaining with visible ridges.
Continuity and power to the motor plugs: All good, both brushes have contact, and the springs are strong.
Control panel: Fully functional—can toggle the green buttons, and the start/stop button responds as it should.
Leads from the control panel to the motor: Power is definitely being transmitted.
I suspect the previous owner didn’t register the product.

Worst-case scenario, I could sell the accessories (hose, hose garage, bottom half, etc.) for at least double what I paid. But I'd much rather have the Midi 1 than stick with my current CT 15.

Any advice would be greatly appreciated!

Thanks in advance, Daniel

 

[tsmi243]

I've been a repair tech for about 20 yrs.  Glad to see you're trying to figure it out!  And I'm glad to help.  Let's start here-

Leads from the control panel to the motor: Power is definitely being transmitted.

1. Clarify this part- "power being transmitted" sounds very clear and simple, but isn't actually a thing.  Your meter doesn't have a "power" setting.  So WHAT did you test, and what were the actual results?  What number, and in what units?  How was the test performed?  Remember I can't see your hands!  Be descriptive.

Assuming you meant "we have voltage"- If you have voltage going to the motor itself, AND if that voltage is present when "under load" (meaning the motor is actually plugged in during your test), then you've isolated the problem to the motor.  Done deal. 

If you're getting voltage but only when the motor leads are undone, then your test really doesn't tell you anything.  Plug everything back in, and back-probe the connections with your meter.  Now do you have voltage when you switch it on? 

2. Can you ohm the motor out? Depending on the result you get, that may give you the answer right away. 

 

[Danieljerloew]

I've been a repair tech for about 20 yrs.  Glad to see you're trying to figure it out!  And I'm glad to help.  Let's start here-

Leads from the control panel to the motor: Power is definitely being transmitted.

1. Clarify this part- "power being transmitted" sounds very clear and simple, but isn't actually a thing.  Your meter doesn't have a "power" setting.  So WHAT did you test, and what were the actual results?  What number, and in what units?  How was the test performed?  Remember I can't see your hands!  Be descriptive.

Assuming you meant "we have voltage"- If you have voltage going to the motor itself, AND if that voltage is present when "under load" (meaning the motor is actually plugged in during your test), then you've isolated the problem to the motor.  Done deal. 

If you're getting voltage but only when the motor leads are undone, then your test really doesn't tell you anything.  Plug everything back in, and back-probe the connections with your meter.  Now do you have voltage when you switch it on? 

2. Can you ohm the motor out? Depending on the result you get, that may give you the answer right away.

Hello Tsmi243,

Thank you for your reply. Unfortunately, it ended up in my spam folder, so I didn’t see it until now. Over the winter, I paused the project, but I’m ready to get back to it and work on getting the vacuum running again.

I’m not an expert with multimeters, and I only have a basic one—nothing fancy like a Fluke.

When I removed the motor, I noticed the fan on top was welded to the shaft due to rust everywhere, when i got the vacuum it was covered in white dust, so i assume previous it has been used by a plaster guy. The motor was also no longer resting on its proper "legs," as they were glued on, and I couldn’t get the motor out at all, ending in 2 broken legs in the housing..

What puzzles me is why the vacuum lights up and the controls work, but it won’t start. I’ll try to follow your instructions and provide numbers and pictures if I can.

I won’t stop until it runs—getting it working again is the goal.

 

[tsmi243]

Awesome.  Stay safe, and DON'T give up  [big grin]

The quickest thing, since you have it apart already, is to just ohm out the motor.  This means set the meter to Ohms (the horseshoe), unplug the two wires going into the motor itself, and then touch those points (on the motor) with the leads.  Basically, the meter sends a little signal out on one of the leads, and listens to see how much of that signal comes back on the other one.  So if your motor is "open winding" internally, it won't get any signal.  If you get pretty much any number, it's likely the motor is NOT the problem. 

But be sure to look at the UNITS on the meter screen.  If it's an auto-range meter, and most are, you may see K-ohms or M-ohms down in the corner of the screen.  Either one is a problem- the motor should have WAY less than 1,000 ohms, so if it auto-ranged itself up that high, something IS wrong with the motor.  Also, make sure you're getting good contact with the leads when you test- because NOT getting good contact could show K-ohms or M-ohms, and mean nothing at all.  You can touch the leads together to see what "zero ohms" looks like.  Press until you get an actual zero- then you know what I mean by "good contact". 

Ohms are the best way to test as a beginner, because you don't need anything plugged in while you do it.  The next step would be to test Volts, which means you'll need to plug the vac back in, and work on it live.  Up to you if you feel capable of that. 

 

[luvmytoolz]

It's worth mentioning that the Midi's were often prone to the copper strands in the mains cable breaking around the clamp/strain relief where it exits the body due to the flexing. The insulation is a very flexible rubber so the effect would often be that it would sort of work and then stop intermittently as the strands were making partial contact then breaking. I've had to do it twice to my wife's Midi and once to mine over the years.

As the very first step to do, I think it would be worth cutting down an extension cord to replace the cable, this is really trivial to do, or you could even just cut the first 2 feet or so off the existing cable and re-terminate it.

Once that's done you've ruled that out as part of the problem.