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Air Con. Blower Motor Brushes worn out? (with pix)

21K views 8 replies 7 participants last post by  CMount 
#1 ·
Background: I'm having a problem with my air con. temporarily not responding: no air comes out at all until after a couple of minutes, and then it works perfectly. Sometimes it'll cut out again for a couple of seconds, but then it'll resume blowing cold air.
I was told to look at replacing the Regulator, but once the air con. is running, all speed settings work correctly (I can vary the intensity of the air coming out depending on what number I switch it to).
The other solution I've read on this forum is to change out the brushes which get worn out over time (not sure how many years these are supposed to last?...:confused:)
I took the blower motor out to inspect it, and I'm not sure how to tell if the brushes are worn out or not. I have no idea how to remove and replace the brushes once the motor is out.
Questions:
1) By looking at these pictures, can you tell if the brushes are worn out?
(the opposite side of the brushes' end was too difficult to photograph, but I could tell it had even less material left)
2) If you do recommend replacing the brushes, how do you remove them from the blower motor?
 

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#2 ·
Hard to tell by those pictures if they are worn out look fairly good but I would have to compare it to a new one. You can take a pencil eraser to the copper plates the brushes run on and clean them with that. Just dont get crazy :D
 
#3 ·
Cleaned the copper plates, but problem still there.

I'm thinking I'll just take a risk and replace the blower regulator hoping that it fixes the problem... it looks easier to replace than replacing brushes, but more expensive...

What are the symptoms of having bad brushes? Will it gradually stop working, or will it be an intermittent problem like I have now? How do you remove the brushes from the motor?
 
#4 ·
If the brushes were no good the motor would not start again. Here how the brushes work. This is a general explanation so it may be different for this motor.

The brushes are spring loaded on the back side and as they wear the springs will keep pushing the brushes forward. Once they are fully worn they will stop making contact against the poles(?) of the motor. Since there is no contact the motor will stop getting electrical energy and will stop. So, I find it highly doubtful that bad brushes will cause intermitent stopping. They are very easy to replace but I am fairly certain they are not your problem.
 
#5 · (Edited)
If the fan is constantly running fine it is not the brushes. From the sounds of it its like the fan stops and starts, can you eleborate? I am an electrician and the theroy of the brushes function is that it induces a voltage to work along with the (poles) of the armature. Basically the voltage is induced and it has to be strong enough to overcome the small airgap in the armature( the inner core that is attached to the fan basket.) This ultimately cause it to spin. If the space between the brush and armature it could affect its movement. If the brushes are gone( picture a brake pad regarding thickness) it will not work.
From your pictures I would say they are in ok shape. Check to see if the armature( fan basket) has and play in it from side to side, A worn out bearing could send it out of alignment which would affect the distance of the brushes. I hope this helps, if I made it to complicated or would like any other explanations feel free to ask!

And if you can get to the contacts of the regulator, ( i havent seen that part) test the output voltage to save your self money, if you are saying it is more expensive.

When you say the aircon is not starting up or just runs intermittent, is this at car startup or mid way through a drive? Im thinking it might be more in the AC compressor or evaporator , Have you thought of a recharge of the system?
 
#6 ·
Thanks for the excellent feedback... it really helps me decide what to do next.

The problem occurs at startup and sometimes during driving. No air will come out, and then all of a sudden it will start blowing cold air again. Sometimes the problem seems to go away for a couple of drives, but then it comes back... when the air condition is working, everything works as it should (speed, on/off, temperature, etc.)
this makes me think it doesn't need freon, and that the problem is electrical.

Being that the problem is intermittent, even if I were to test the voltage on the regulator, it wouldn't necessarily produce bad results, so I decided to take a risk and order the $120 blower regulator.

I'll report back as soon as I install it.
 
#8 ·
Not for the SLK, but I had a similar issue with my 210 chassis. Was it the regulator or the blower motor? What I did was remove the blower motor and hook it up directly to a 12v battery for just a few seconds - damn near blew me out of the garage. :) That told me that the blower motor was good. I then replaced the regulator and all has been well for over a year.
 
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