Dewalt Dc390 cordless circular saw ,not working

8 years 3 months ago #1453 by Globalmark
Hi all

Hopefully someone can help , I got a dewalt dc390 cordless circular saw , and seems to run slow speed and has lack of strength when cutting , battery also seems to get very hot and takes ages to cool down .
Now seems like a low power battery but I have 4 batteries 2 of which are new and same happens with each . I can just about cut a small piece of wood by using all batteries but each battery last max 30 sec - 1 min .
Obviously there is some fault. With the circular saw . Does anyone have any idea what might be the cause .
Spare parts are readly available and I can change myself but need to know how to test what part so I can order correct part ?
Motor , armature, brushes ( but no sparks that I can see) etc

Any suggestions much appriciated
Thanks Mark

Please Log in or Create an account to join the conversation.

8 years 3 months ago #1456 by MTR-Admin
Replied by MTR-Admin on topic Dewalt Dc390 cordless circular saw ,not working
Thanks for the post Mark,

To me, it sounds like a defective field/armature causing excessive load on the batteries.

You may want to contact DeWalt directly at 800-433-9258 and ask a service technician how to test this. You can with a multimeter if you have one, but it may be easier to speak with an authorized service technician regarding this issue.

- MTR

Please Log in or Create an account to join the conversation.

8 years 3 months ago #1461 by Globalmark
Replied by Globalmark on topic Dewalt Dc390 cordless circular saw ,not working
Hi MTR

I found some info via Google and tested the Amps the motor was drawing , and on a fresh battery is approx 7-7.3A and settles on 5.56A , tested this several times and always similar .
However I don't know approx what it supposed to be so don't know if correct .

I have emailed Dewalt and they replied saying maybe motor , take to service centre . But where I live is a 300klm return trip and cost of repair would not be worth it , but I can buy a new armature and or magnet ring online and fit myself would be OK ..
So any more ideas appriciated .

Thanks Mark

Please Log in or Create an account to join the conversation.

8 years 3 months ago #1462 by MTR-Admin
Replied by MTR-Admin on topic Dewalt Dc390 cordless circular saw ,not working
Mark,

It does sound like your motor is on its way out, so replacing the Motor may fix your problem. I can't guarantee it of course, being I'm not there to diagnose it myself, but this is what it sounds like by what you've been able to explain so far.

- MTR

Please Log in or Create an account to join the conversation.

8 years 3 months ago #1463 by Globalmark
Replied by Globalmark on topic Dewalt Dc390 cordless circular saw ,not working
Hi MTR

I JUST HEARD BACK FROM Dewalt service not much info but they confirmed the motor should draw 9.2A , and say probably the motor which would need replacing , but also mention that it could be the switch causing it .
Do you know how I can test if it is the switch ?
I would guess bypass switch with battery and check the Amps there and hopefully read 9.2A and if not would confirm its the motor not the switch ?
But not sure if this is correct way to test ?
Thanks Mark

Please Log in or Create an account to join the conversation.

8 years 3 months ago #1464 by MTR-Admin
Replied by MTR-Admin on topic Dewalt Dc390 cordless circular saw ,not working
Mark,

You can bypass the switch and apply direct voltage to it for a short period, yes. Not having the engineering drawings of the switch, I don't know if there is a voltage reducer in the switch, however.

Hopefully the DeWalt service representative can give you this information also.

- MTR

Please Log in or Create an account to join the conversation.

Moderators: MTR-Admin
Time to create page: 0.120 seconds