Author Topic: New brushes in blower motor  (Read 3991 times)

1980sdga

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New brushes in blower motor
« on: 22 June 2012, 12:35 AM »
My AC blower went south so I pulled it to check the brushes. Here's what I found:



Those little nubs are the old brushes  :o

I figured out how to pull the motor apart by separating the back from the can. The back interlocks with the can with these little tabs:





The bottom slot is where the board that holds the brush assy. sits.

If you are careful you can gently pry it apart and re "arch" the tabs on the back so it will lock back together by "flattening" the tabs by tapping with a hammer. I had to do this several times...



I chucked it in a drill press and tidied it up:



New brushes:



Anyone want to school me on those components? It looks like 2 coils and maybe a cap (?) between the pos and ground?

I don't have a part # for the brushes. They were some extras that came with a Chinese power tool that I adapted.

So far it seems to work fine on the bench but it gets pretty hot. I guess that's why they have the little cooling hose?
Jon


Little by little I have grown fond of the infamous Auto Temp II we have in our 116's

WGB

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Re: New brushes in blower motor
« Reply #1 on: 22 June 2012, 12:53 AM »
Apart from any electrical issues the most common problem is that they start to squeak on low fan settings.

A new fan motor for the LHD US system was easy and economical to purchase a year or two ago and would give you a permanent fix.

Here is a posting I did 18 months ago showing fitting a LHD fan into a RHD HVAC system

http://forum.w116.org/mechanicals/installing-a-lhd-climate-control-fan-in-a-rhd-hvac-car/msg71575/#msg71575


Bill

philpot

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Re: New brushes in blower motor
« Reply #2 on: 22 June 2012, 02:06 AM »
The coils look like thick copper wire. I reckon in conjunction with the cap they form a suppression circuit to stop any arcing of the brushes as they sweep between each bank on the commutator. Make sure you clean any copper out of the grooves on the commutator before you put it back together.
I presume you have checked to make sure the pigtail lead off the brush won't get caught as the brush is pushed back in its housing by the commutator?
Is that just brush dust on the cap legs where they enter the body?

Tony66_au

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Re: New brushes in blower motor
« Reply #3 on: 22 June 2012, 06:01 AM »
 


  Make sure you clean any copper out of the grooves on the commutator before you put it back together.
[/size]
[/size]VERY important because once the gap between is gone your fan has run out of life, normally youd mill the contact areas up in a small shop lathe to ensure good brush contact but from the pics supplied? I dont think it has much life left.
[/size]
[/size]Id honestly look at a new unit.
[/size]
[/size]Tony

philpot

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Re: New brushes in blower motor
« Reply #4 on: 22 June 2012, 11:31 PM »
Yeah, I'm with Tony. Particularly given the uneven nature of your commutator!
That's the last place you want electrical sparks..hard to stop a cabin fire once its on!

1980sdga

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Re: New brushes in blower motor
« Reply #5 on: 23 June 2012, 09:19 AM »
I have a new one on order but I like fooling with stuff  ;D

The coils are just heavy enameled wire wound around a black pin and the "cap" is a little rectangular plastic box. It doesn't look like any type of cap I'm familiar with...
Jon


Little by little I have grown fond of the infamous Auto Temp II we have in our 116's

koan

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Re: New brushes in blower motor
« Reply #6 on: 23 June 2012, 05:35 PM »
The black pin in the coil is probably a lump of ferrite or similar to increase the coils inductance. The cap could be anything.
Boogity, Boogity, Boogity, Amen!

JasonP

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Re: New brushes in blower motor
« Reply #7 on: 23 June 2012, 06:31 PM »

Don't these coils (inductors) together with the capacitor (cap) produce the AC output signal to a specified frequency? 
1979 300SD
Color: 623H "Light Ivory"
1979 300SD
Color: 861H "Silver Green Metallic"
1977 280 E
Color: 606G "Maple Yellow"
-------------------------------------------

koan

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Re: New brushes in blower motor
« Reply #8 on: 24 June 2012, 05:34 PM »
Don't these coils (inductors) together with the capacitor (cap) produce the AC output signal to a specified frequency?

No, not in this situation. Inductors and capacitors do form AC circuits that resonate at a specific frequency but that's not their purpose here.

Boogity, Boogity, Boogity, Amen!

WGB

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Re: New brushes in blower motor
« Reply #9 on: 24 June 2012, 06:31 PM »
I would think the capacitator is for radio noise suppression.

Anyway I can assure you a US spec motor works just fine in a RHD HVAC system spinning the wrong way as I was driving my 6.9 over the weekend.

Bill

koan

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Re: New brushes in blower motor
« Reply #10 on: 24 June 2012, 08:41 PM »
Anyway I can assure you a US spec motor works just fine in a RHD HVAC system spinning the wrong way as I was driving my 6.9 over the weekend.

Wouldn't risk going to far north though the coriolis force may be too much and force your car to veer off the road.
Boogity, Boogity, Boogity, Amen!

WGB

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Re: New brushes in blower motor
« Reply #11 on: 24 June 2012, 09:08 PM »
Anyway I can assure you a US spec motor works just fine in a RHD HVAC system spinning the wrong way as I was driving my 6.9 over the weekend.

Wouldn't risk going to far north though the coriolis force may be too much and force your car to veer off the road.

Thanks Koan - I'll keep that in mind next time I try a North-South Circumnavigation of the globe :)

Bill

JasonP

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Re: New brushes in blower motor
« Reply #12 on: 24 June 2012, 09:18 PM »

Choke coil!

This was bugging me, since I'm a former EE, so I finally found what it is.



Quote
To make automobiles more energy-efficient and lightweight, an increasing number of their components have become electrically driven.. For this reason, electric motors are used not only for traditional devices like windshield wipers, but also for power steering, fuel pumps and so on. Some DC motors use brushes to rectify the current, but because such brushes are repeatedly contacting and separating from commutators, sharp fluctuations in electric current cause noise and spark noise (Fig. 2). If such noise flows through the power line to other parts, it could have an adverse effect. While it also depends on motor speed, this noise can range widely in frequency from hundreds of kHz to hundreds of MHz, making it necessary to take adequate noise countermeasures.

Found it here:
http://www.murata.com/products/emicon_fun/2012/02/emc_en14.html


1979 300SD
Color: 623H "Light Ivory"
1979 300SD
Color: 861H "Silver Green Metallic"
1977 280 E
Color: 606G "Maple Yellow"
-------------------------------------------

Tony66_au

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Re: New brushes in blower motor
« Reply #13 on: 24 June 2012, 10:31 PM »
Anyway I can assure you a US spec motor works just fine in a RHD HVAC system spinning the wrong way as I was driving my 6.9 over the weekend.

Wouldn't risk going to far north though the coriolis force may be too much and force your car to veer off the road.


LMAO!

You Sir... are a crackup!