6

I have a circular saw that quit working for no obvious reason.

I cut a board and sat the saw down to get another board.

When I tried to cut the next board, the saw wouldn't work. Pull the trigger and nothing happens.

Is a circular saw DIY repairable? If so, where would I start looking?

EDIT

Sorry, here is what I've tried.

  • Verified outlet has power.
  • Removed blade and blew out all debris (doesn't work with blade out either).
  • Jiggled the cable. :)
  • Have you done any basic troubleshooting yet, like verifying the device is getting power (maybe you tripped a breaker)? – Steven Apr 14 '12 at 18:38
  • @Steven I updated my question with things I've tried. It's been this way awhile, so it's been tried on several different outlets. – aphoria Apr 14 '12 at 18:47
  • can you turn the motor by hand? – ratchet freak Apr 14 '12 at 19:02
  • What make/model, and how old? – Jason Apr 14 '12 at 19:50
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    If jiggling the cable doesn't work, then we have one last resort before we need to call in an expert. Did you try thumping it? – Chris Cudmore Sep 24 '13 at 17:38
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Here's a first-stab at a troubleshooting guide:

With the unit unplugged and/or the battery removed:

  1. Visually inspect the tool...

    1. Is anything potentially jamming a mechanism?
    2. Are the air vents clogged?
    3. Has the unit been exposed to too much dust, ash, water and/or fine sawdust?
    4. Is the case discolored or cracked at any spot?
    5. On the power cord, is the insulation cracked at any point or is one or more strain-reliefs damaged or missing (especially where the cord enters the tool)?
    6. Are the plug contacts reasonably straight and untarnished?
    7. Is a fuse or reset button present? Is it blown or popped out?
    8. Was the tool used until it might have become too hot? Many tools have a safety, over-temperature shutoff; wait an hour for it to reset.
    9. Is the safety switch/lock, if present, installed and/or on?
    10. If the unit came with a grounded plug, be sure that it's undamaged and that the power plug really is a properly wired grounded outlet. Use one of those circuit checkers you can get for $2.
    11. Has an oily, greasy, or varnishy fluid dripped or oozed out of any part of of the unit? Grease could indicate bearing failure. Other oozings would point to catastrophic motor damage, or sometimes electronics failure or starting capacitor failure.
  2. Does the tool rotate/reciprocate relatively normally when moved by hand?

  3. Does the the power switch feel normal? Usually a busted switch will feel "off" (Pardon the pun.)
  4. If you are comfortable with an ohmmeter, you can use it to do basic checks on the cord and switch. Note that it is possible for a circuit to look okay with the meter and still be bad under load -- or for control electronics to be bad.


With the unit powered:

  1. Does the motor hum or smoke when turned on? (Of course, Immediately switch it back off if it does this.)
  2. Does a circuit breaker trip?
  3. Do you feel an electric shock?
  4. Does the motor arc excessively?
  5. Any unusual noises? Humming, or squealing?

If the visual inspection is failed, it should be obvious what to do.

  1. For a damaged cord, replace it. Do not attempt to repair it.
  2. If the case is plastic and is discolored anywhere, it has likely degraded to the point that the tool is either unsafe or it's just not worth repairing. Some uniform case discoloration due to age and UV exposure can be okay -- as long as the case is not also cracked or brittle.

If the switch feels funny and/or nothing happens when it is turned on, then it could well be a busted switch -- which is pretty common. You can sometimes get replacement switches at a reasonable price.

If the motor arcs excessively (a little visible arcing is normal), the brushes may need replacing. Do not run the tool if you suspect brushes, you can permanently damage the motor.

If the motor hums or smokes, it's typically one of these problems:

  1. Something is mechanically jammed.
  2. Bad switch.
  3. Bad power cord.
  4. Bad control electronics, if any.
  5. Bad, broken, or burnt internal wiring.
  6. Bad brushes or damaged commutator plates.
  7. Bad starting capacitor (if used).
  8. Bad starting coil.
  9. Improper outlet voltage and/or grounding.
  • Great answer! I haven't had time to run through your entire list yet, but I can't imagine a more comprehensive list. – aphoria Apr 16 '12 at 1:54
  • Thanks! If you do end up fixing it, I'd love to know what it turned out to be. – Brock Adams Apr 16 '12 at 2:08
  • Here are a couple of links to websites for power tool repalcement parts. They also have exploded views showing all the part numbers. link and [link] (toolpartsdirect.com/toolparts.html) – RSMoser Apr 17 '12 at 17:37
  • Thank you, @RSMoser. Note that the first site was already linked in the answer as well. – Brock Adams Apr 17 '12 at 21:23
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    Do you feel an electric shock is not necessarily something I like to see on a troubleshooting list. – Chris Cudmore Sep 24 '13 at 17:39
3

I just had a similar problem. It turned out to be the switch. I took it apart, opened up the switch/trigger and it was full of dust. I blew it out and works fine now. While I had the casing open, I also took the opportunity to replace the brushes.

  • 1
    switch would have been the first thing I would have looked into as well. – mike Sep 24 '13 at 6:10
1

I had the same issue with my saw and traced the problem down to the switch. Pulled it apart and found the contacts had burnt out due to over heating. $14.00 fix by replacing the switch.

0

To zero in on the specific problem as described: Looking at how the problem appeared, i.e., saw was working one minute and not the next, first suspect is the switch but I always look at easiest things first.

  • Outlet power would be first in case a breaker tripped.
  • I'll assume the cord won't suddenly be broken when it was just fine and isn't visibly distressed. Sure broken wire strands can be hidden but they'll usually show up as intermittent cutting out at first.
  • Switches, on the other hand, at least in the case of a Skil Model 77 worm drive, having spring contacts inside that can break after getting fatigued, may suddenly die or, if barely making contact, work sporadically. Switches, at least the older ones, may still feel normal with a good strong click. To check this, remove the right half of the handle. Checking voltage where cord joins the switch tells you if the cord is OK. Checking continuity across the switch with trigger pulled (WITH SAW UNPLUGGED) tells you if it's the switch. You could pop open the switch to look inside but there's not much you can do except see how they work and why they have a lifespan.
0

Great responses so far. I would add that I confirmed a bad switch on a Miter box saw by CAREFULLY jumping the switch. I just un-screwed the wires from the switch and touched them together. (Insulated plier handles would be a good precaution!) The saw started immediately. This was easier on a Miter box as it is bolted down. Care must be taken if you are trying this with a hand held circular saw sitting on a bench. Make SURE the guard is down and completley covering the blade for safety. If possible, find a way to clamp it to your workbench top before starting it up or at least have someone else hold it steady for you. By looking at the switch I was able to I.D. the brand and model and found a suitable non OEM replacement switch for under $10 online. Pay attention to what wires go where BEFORE you take them off and mark them with tape or write on the switch with a marker. Cell phone photos help on re-assembly, too. Some switches have a mini-schematic printed on their label, so check to make sure you have it wired correctly. If you can turn a screw driver you can do this! A Volt Ohm meter is also a good troubleshooting tool to determine if you have power and to where. Always disconnect the power unless you are checking to see if you have it!

  • This answer could use some formatting. – Tester101 Dec 17 '15 at 17:28
0

when standing in front of this items, to the right of the motor, there is a black like ring (it look like a fuse holder), inside there is a piece of magnet connected to a spring, make sure the spring has been placed properly inside the housing. if not then your going to have this issue of working and not working. i just reset mine back into the housing and it came right on. Also it would be a good ideal to go and get a couple of replacements from lowes, i found out that the magnet wears out over time and use. Hopefully this works for you as it did for me.

REPLACING CARBON BRUSHES (FIG. 37) Replace both carbon brushes (3) when either has less than 1/4 in. length of carbon remaining, or if the spring or wire is damaged or burned. To inspect or replace brushes, first unplug the saw. Remove the black plastic cap (2) on the side of the motor (1). Use caution when removing the cap because it is springloaded. Pull out the brush and replace. Replace for the other side. To reassemble, reverse the procedure. Press the metal part of the carbon brush in the hole where the carbon part fits. Tighten the cap snugly but do not overtighten. NOTE: To reinstall the same brushes, first make sure the brushes go back in the way they came out. This will avoid a break-in period that reduces motor performance and increases wear

  • Please use the edit link underneath your post if you want to update it; don't post multiple partial answers. I've incorporated your other post into this one, and marked it as a quotation since that's what it appears to be. Please see the help center for more information about how to cite other people's work, the tour for an overview of how this site works, and How to Answer for more information about answering questions. Thanks and welcome to the site! – Niall C. Sep 3 '16 at 0:08

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