Makita multitool stalling and burning smell

[phatboy]

Hi all, Looking for a bit of help with repairing my Makita TM3000C multitool.

I was using it a couple of weeks ago, and it suddenly slowed down. I left it to cool off, but upon trying again it spun very slowly as seen through the casing, and started to make a mild burning smell.

My first thought was to change the brushes, as the tool is 10 years old. The old brushes looked basically new! I cleaned the armature with 600grit wet and dry, and fitted new brushes, but still the same.

The motor does spin freely when disassembled (As per the picture), so I'm a bit lost!

Any help much appreciated in reviving it.

Tim

 

[Harry Bloomfield]

The over-heating, will have damaged the insulation, and caused shorted turns. It is basically scrap.

 

[phatboy]

The over-heating, will have damaged the insulation, and caused shorted turns. It is basically scrap.

Oh no!

What causes this sort of thing to happen? I had been using it for about half an hour without break.... did I kill it or just bad luck?

 

[Harry Bloomfield]

Oh no!

What causes this sort of thing to happen? I had been using it for about half an hour without break.... did I kill it or just bad luck?

Lack of mechanical sympathy. It must have become very hot in use, you must have noticed that heat, but chose to ignore it and carry on - rather than allowing it to cool down. Portable drills, multitools, jigsaws, etc., are neither designed, nor expected to run continuously. The user, needs to be aware of their limitations, keep a close eye on their temperature, and allow them time to cool down.

The problem with motors, is that often they include a cooling fan, on the motor shaft. The more heavily loaded the motor, the slower it runs, the more heat it generates, and the slower the cooling fan runs, and the less effective the cooling. Sometimes, it is worth just running the item, without any load, to allow the fan to cool it down.

 

[jj4091]

Dont' know how much a new one is but you can get a new armature and field coils for approx. £80 https://www.mtmc.co.uk/product.aspx...X-zxvSFmIGDXKX7MsddS9XNlROv7mq6kaAnOcEALw_wcB
Make sure you order for the correct voltage if you go down that route

 

[phatboy]

Lack of mechanical sympathy. It must have become very hot in use, you must have noticed that heat, but chose to ignore it and carry on - rather than allowing it to cool down. Portable drills, multitools, jigsaws, etc., are neither designed, nor expected to run continuously. The user, needs to be aware of their limitations, keep a close eye on their temperature, and allow them time to cool down.

The problem with motors, is that often they include a cooling fan, on the motor shaft. The more heavily loaded the motor, the slower it runs, the more heat it generates, and the slower the cooling fan runs, and the less effective the cooling. Sometimes, it is worth just running the item, without any load, to allow the fan to cool it down.

I didn't notice the heat, although I was wearing gloves. But I was using it for sanding, so no real intense pressure or anything. When it slowed, I did leave it an hour or so to cool - running it with no load didn't occur to me, but I also fear it would have been worse if it was already struggling.

 

[phatboy]

Dont' know how much a new one is but you can get a new armature and field coils for approx. £80 https://www.mtmc.co.uk/product.aspx...X-zxvSFmIGDXKX7MsddS9XNlROv7mq6kaAnOcEALw_wcB
Make sure you order for the correct voltage if you go down that route

Thanks, it seems a new one is worth £130ish still. I have found one without box and accessories on eBay for £38, which may be the best course of action, as all the accessories I have are fine. Ill think about it, as I do also have a Bosch 18v one, but this is my preferred one usually.

 

[Harry Bloomfield]

When it slowed, I did leave it an hour or so to cool - running it with no load didn't occur to me, but I also fear it would have been worse if it was already struggling.

Once the heat build-up has turned to damage of the windings, then it is all too late. Running it to cool it, or leaving it to cool down will not recover it. Other than the heat generated, a second clue is the smell - as a warning that you ought to give the item a rest.

 

[opps]

Lack of mechanical sympathy. It must have become very hot in use, you must have noticed that heat, but chose to ignore it and carry on - rather than allowing it to cool down. Portable drills, multitools, jigsaws, etc., are neither designed, nor expected to run continuously. The user, needs to be aware of their limitations, keep a close eye on their temperature, and allow them time to cool down.

The problem with motors, is that often they include a cooling fan, on the motor shaft. The more heavily loaded the motor, the slower it runs, the more heat it generates, and the slower the cooling fan runs, and the less effective the cooling. Sometimes, it is worth just running the item, without any load, to allow the fan to cool it down.

In the old days, tools often quoted the maximum permissible run time and wait times before using them again.

AFAIK, most of my festool sanders are rated as "industrial", meaning that they can be run "continuously". That said, yes, I guess that it is assumed that the user will not apply excessive pressure .

BTW- I am not suggesting that @phatboy was guilty of pushing the tool too hard, but at that price point, Makita clearly cut some corners. A friend who restored sash windows used to get through about 2 of those multitools a year. He did push it hard though. 6 months in, it would burn out. He would take it back to Screwfix, get a full refund and buy another (with a new 12 month warranty ). He did that for about 4 years. When he took the last one back, the manager told him that it was the last time that they would allow him to do that. Rather than paying £400+ plus for a Festool Vecturo or the Fein Supermax, he was happy to pay a one off of less than £100 which saw him through 4 years.

 

[securespark]

When you buy something, it has 12m warranty. If it falls apart and is replaced, you are still on that same 12m timeframe.

So, if your first item is replaced at 10m, you have 2m warranty remaining on the replacement.

 

[cdbe]

Some places, eg Aldi, Lidl and presumably Screwfix, just give you a refund in the event of a warranty claim so you just buy another (with a new 3 year/12 month warranty).