Bosch 4000 tablesaw suddenly ran backwards and died
Was operating my Bosch 4000. After ripping 3 thin pieces, the unloaded motor started to run backwards, then died. Won't start now. Outlet is fine. Checked the bearings, which look fine. This saw has been very reliable for the last 4 years. Could this be a capacitor or controller issue?? Thanks for any help.
Re: Bosch 4000 tablesaw suddenly ran backwards and died
I had a customer bring me a saw with this same problem. All components tested OK on my growler. I went on a limb since the speed control and the armature tested OK. I replaced the feild since to me it seemed to be the only component that could cause the motor to run in reverse. Tool now works properly and have had no more problems with the tool.
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Possibly something has jammed inside the motor housing although unlikely.
Electric brake seized perhaps?
Carbon brushes need replaced?
These saws (and the newer 4100) have a history of motor problems, with the field winding and electronic motor speed control being the most common points of failure. If you go to an online tool parts supplier like toolpartsdirect- Bosch 4000 saw you will see a list of the parts available, as well as the most commonly ordered parts.
I have found the most common issue is a bad field with the second being a bad rear armature bearing and last being a bad speed control.
Most of the time slow speed or even running backwards is a bad field (part #2 on the breakdown) #1619PA5590
Remove the cap on the end of the motor & the 2 carbon brushes.
Remove the 4 screws holding the motor to the frame and pull it straight off.
Check the bearing on the end of the armature to ensure it is not frozen or stiff. If it is also check the rubber boot that sits over the bearing and the motor housing itself to ensure it is not melted.
I've worked on some table saws with problems like you describe, a couple needed a new speed control unit (Bosch PN 2610997306) in the motor. If all the wiring to and inside the motor is OK and not shorting out anywhere, that's the next part you should look at.
You can find the 4000 manuals and parts diagram at bosch tools online. You will need a new armture Bnew bushes and possibly field. I would also replace the bearings and motor speed control circuit board.
Bosch does not sell the motor assembly.
Turn unit upside down and remove the Plastic body - approx 6 screws.
Thake a digital camera and take LOTS of pictures of dissassembly as you will need them later. Blow unit clean and work neatly keeping all parts in labeled bins for reassembly. Don't attempt this job when your pressed for time.
Before you start check to see if this machine is still under warranty!!
Call customer support listed on website if you run into a problem.
Good Luck !!
I found that the remaining problem was a intermittent at the switch, which disassembly and cleaning resolved.
Tilting the motor / blade assembly down allows access from below, to the 3 screws fastening the controller circuit board cover on the brush end of the motor. From there, one can easily test exposed wires for power supply, see that brushes are contacting and clean accumulated sawdust.
Replace the field coil. I'm going to bet its a Model 4000. I have done about 100 of these saws in the last couple of years and my customers always complain of the same problem, "the saw was running backwards"
Change the armature back bearing while you have it apart, they always seize eventually.
Is it spinning the blade at all? If it is then it is unlikely to be an electrical fault. Have you considered a motor bearing fault? If the motor bearings are worn, it could turn freely by hand, but when powered up it would stutter and stall. The motor is basically a big electro-magnet so if the armature has enough lateral movement, when it is magnetized it could rub against the stator.
If the machine is buzzing, but not spinning the blade it is more than likely going to be caused by a faulty capacitor as this is the component that gives the motor the initial 'kick' in the right direction to get it spinning.