Question about Bosch Brute Breaker Hammer 11304

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We have a couple of brutes that hit slow, I've tried rebuild kits, field coils and armatures. None of these seem to work. Amp drawn normal. Any Ideas???

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Sounds like you have too much suction in the hammer cylinder. The hammer may be getting stuck at the top of the cylinder. Inspect to see if the hammer beat piece will slide out of the hammer cylinder. There may be too much grease behind the hammer causing suction at the up stroke. There may also be scarring inside, so inspect to see if the hammer beat piece slides smoothly. Hope this helps.

Posted on Sep 14, 2009

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It sounds mechanical. The rotating cam that turns to hammer

Posted on Jun 26, 2009


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Posted on Jan 02, 2017

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1 Answer

Mobility scooter motor gets very hot. batteries run down quickly

Hi get the motor field coils & armature checked for shorts u can check the field coil with a multimeter / it would b advisable to get the armature checked on a ( GROWLER )....cheers

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I overheated my Makita 9557PB angle grinder. I replaced the brushes. Bearings seem ok: the motor assembly turns freely, smoothly, and quietly. The running motor is slow, with a loud "grinding" sound.

Measure the value difference in Ohm between the carbon brushes on the armature there are some collectors in the commutator give an other ohm value if compared to other collectors in the comutator of the armature . if measure turn the blad very slow so the collectros can be positioned to measure the ohm difference. range to measure 0-200ohm on ohmmeter.
If only one brush made trouble ( much more sparking ) then the electric field is not in ohm value balance, control always if there are slide contacts used they are solid. on the field. Measure the difference. between the 2 field coils of the electric field . if its also different replace allways the field and the armature if thats also have problems (BUT DON,T FORGET to order a new drive gear for the armature and new brushes. !!!

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1 Answer

My hitachi jackhammer runs slow and gets hot

The armature AND electric field must together replaced to get a safe working again, and the defect will not repeat if it be shure have its operating hours on it and give a full service.

May 24, 2014 | Bosch Brute Breaker Hammer 11304

2 Answers

New brushes are sparking real bad

It sounds like the armature is bad. It should have an even dark ring around the bars of the armature commutator where the brushes ride. If one or two of the bars is discolored above and/or below that it could easily be bad. It could also be pitted between a couple of bars. Normally the space between the bars is even all the way around and nice and "clean cut" looking. If you have access to an armature growler you can test the armature. Hope that helps.

Jan 21, 2014 | Skil Circular Saw 7 14" HD77 Worm Drive

1 Answer


To fully test the armature you need to remove it and use a bit of kit called a 'growler'. Most powertool service shops (especially manufacturer approved ones) will have one of these. You can get a fair idea form a couple of visual inspections too though.
It is best to remove the motor housing so you can see the rear of the armature clearly (the commutator). First of all though, before you completely remove the motor housing you will need to remove the brushes. The running faces of the brushes should be nice and smooth, if they are pitted and and rough looking across the entire running face then this shows that the motor has been sparking too much and the armature is most likely to be faulty. If the running faces of them is only pitted and dull halfway across this would indicate that the field coil is faulty and would need replacing. Once you have checked this, if you want to double check the armature, you should continue to remove the motor housing. the field coil will usually stay inside the housing when you remove it which is good as it means you don't have to disconnect any wires. You need to visually inspect the copper segments at the end of the armature (the commutator). All the segments should be of a similar colour and not too dark, although there will be carbon 'burnt' onto them. The gaps between each segment should be pretty much straight and all the same between each bar. If an armature is shorting out you will normally find a couple f the segments have started to raise slightly. These segments will have an abnormal gap between them and be darker or appear mire burned than the others. If they all seem fine, the only other check you can do on an armature is with a growler so you would have to get in touch with your nearest repair shop and see if they can help you.

Sep 13, 2013 | Bosch Skil HD77 7-1/4 in. Worm Drive...

1 Answer

@runs hot motor feels slow doesnt hit hard

Bosch brute is made to work all day every day and will continue to do so if it is not over or under powered and properly lubed. If not powered correctly, motor will not turn at full rpm, get very hot and burn brushes to point that auto stop feature will stop motor (brush will push away from armature, or burn switch). The hammer will overheat if too long or wrong gauge of cord is used. Also if run on generator with voltage /cycles incorrect. Under normal use, motor will not get very hot. Another problem with overheating is that the grease will melt out of range to do any proper lubrication. If you are sure that it is getting proper voltage /amps then may need lubrication or bearing work. Remove bearing cover and turn armature by hand. It should be easy to turn. If stiff, suspect bearing/grease. With amp meter connected, check amp draw and compare to rated amps.

Mar 26, 2011 | Bosch Brute Breaker Hammer 11304

2 Answers

I have a bosch brute hammer drill, that just stopped working after 2 hours of breaking up concrete and rock. It is brand new, and worked fine to start with, but then gradually took longer and longer to...

Take it back as it is still under warranty. If there was anything you could do other than letting it cool down it would be in the instructions.( which you have since it is brand new.)

Mar 14, 2011 | Bosch Brute Breaker Hammer 11304

1 Answer

220 volt was applied to motor due to faulty 220/110 V adapter. How can I troubleshoot motor

The first thing to do is smell it. If it smells burned, it is probably fried. If it isn't working after being plugged into 220, there won't be a fix. Armatures & field coils aren't available for these.

Nov 07, 2009 | Dremel 300-N/55 300 Series Tool Kit

2 Answers


450 out of 600 what? sounds like you have somthing drawing power need an amp meter. remove key and leave window down. disconnect negitive battery cable and connect meter between the negitive cable and negitive termainal on the battery should see around 2.5 milliamp draw or less may take 1/2 hour to get to this point. also if this vechile is not driven often this could be the problem

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1 Answer

Drill slowing down under load

indicates either field windings or armature problem
at 12 years parts will be hard to come by

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